diff --git a/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ApiResponse`1.mustache b/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ApiResponse`1.mustache
index 3ac107fa7133..3cd0aaf7d0ff 100644
--- a/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ApiResponse`1.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ApiResponse`1.mustache
@@ -49,6 +49,11 @@ namespace {{packageName}}.{{clientPackage}}
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -106,6 +111,11 @@ namespace {{packageName}}.{{clientPackage}}
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -144,6 +154,7 @@ namespace {{packageName}}.{{clientPackage}}
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -167,6 +178,7 @@ namespace {{packageName}}.{{clientPackage}}
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -178,6 +190,7 @@ namespace {{packageName}}.{{clientPackage}}
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
     {{#x-http-statuses-with-return}}
diff --git a/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ClientUtils.mustache b/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ClientUtils.mustache
index 357d2197cd97..6e7f9809f237 100644
--- a/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ClientUtils.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ClientUtils.mustache
@@ -18,6 +18,7 @@ using {{packageName}}.{{modelPackage}};
 {{/-first}}
 {{/models}}
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 {{>Assembly}}namespace {{packageName}}.{{clientPackage}}
 {
@@ -311,6 +312,36 @@ using System.Runtime.CompilerServices;
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                {{#net80OrLater}}
+                    return [];
+                {{/net80OrLater}}
+                {{^net80OrLater}}
+                    return Enumerable.Empty<MediaTypeWithQualityHeaderValue>();
+                {{/net80OrLater}}
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                {{#net80OrLater}}
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+                {{/net80OrLater}}
+                {{^net80OrLater}}
+                    return new [] { MediaTypeWithQualityHeaderValue.Parse("application/json") };
+                {{/net80OrLater}}
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/api.mustache b/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/api.mustache
index 2ebe38a2919e..f75235833fbe 100644
--- a/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/api.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/api.mustache
@@ -8,6 +8,7 @@
 {{/nrt}}
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 {{#net80OrLater}}
 {{#lambda.uniqueLines}}
 {{#operations}}
@@ -20,6 +21,7 @@ using System.Linq;
 {{/lambda.uniqueLines}}
 {{/net80OrLater}}
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -605,10 +607,10 @@ namespace {{packageName}}.{{apiPackage}}
                     {{#produces}}
                     {{#-first}}
 
-                    string{{nrt?}} acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     {{/-first}}
                     {{/produces}}
                     {{#net60OrLater}}
diff --git a/samples/client/petstore/csharp/generichost/latest/ComposedEnum/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/latest/ComposedEnum/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 1621a6122d6f..378e7f3a86ae 100644
--- a/samples/client/petstore/csharp/generichost/latest/ComposedEnum/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/latest/ComposedEnum/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 }
diff --git a/samples/client/petstore/csharp/generichost/latest/ComposedEnum/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/latest/ComposedEnum/src/Org.OpenAPITools/Client/ClientUtils.cs
index c72d032fc8f1..3c7e3f8809dc 100644
--- a/samples/client/petstore/csharp/generichost/latest/ComposedEnum/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/latest/ComposedEnum/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -19,6 +19,7 @@
 using System.Text.RegularExpressions;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -226,6 +227,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Api/DefaultApi.cs
index f551e16fc2f6..addbd3372e39 100644
--- a/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
diff --git a/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index d7a8aa9e0b7b..0b9df641d68f 100644
--- a/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 }
diff --git a/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Client/ClientUtils.cs
index 4d0ea7aa7bcc..78e03361249d 100644
--- a/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/latest/HelloWorld/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -19,6 +19,7 @@
 using System.Text.RegularExpressions;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -220,6 +221,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs
index 681cc7ac29cc..1a2db06bc669 100644
--- a/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -253,10 +255,10 @@ public async Task<IIconsApiResponse> IconsAsync(Option<IconsSizeParameter> size
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index f786ed6177f6..d28bf0591331 100644
--- a/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index 3b7bf799d5f0..3cd28f988823 100644
--- a/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/latest/InlineEnumAnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -19,6 +19,7 @@
 using System.Text.RegularExpressions;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -222,6 +223,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Api/DefaultApi.cs
index 40a0a9a1b91b..80d4d815da60 100644
--- a/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
diff --git a/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 5c0e0a406103..1e4685882e8f 100644
--- a/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 }
diff --git a/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Client/ClientUtils.cs
index afcf529d354a..db80cd11d531 100644
--- a/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/latest/OneOfList/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -19,6 +19,7 @@
 using System.Text.RegularExpressions;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -220,6 +221,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Api/APIKEYSApi.cs b/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Api/APIKEYSApi.cs
index b69c228b8aa0..fd57946c5dd0 100644
--- a/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Api/APIKEYSApi.cs
+++ b/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Api/APIKEYSApi.cs
@@ -13,7 +13,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
diff --git a/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Api/APIKeys0Api.cs b/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Api/APIKeys0Api.cs
index 34ae08c7617a..f556390bafd1 100644
--- a/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Api/APIKeys0Api.cs
+++ b/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Api/APIKeys0Api.cs
@@ -13,7 +13,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
diff --git a/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Api/ApiKeys1Api.cs b/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Api/ApiKeys1Api.cs
index c447103ad329..805dbed90ca5 100644
--- a/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Api/ApiKeys1Api.cs
+++ b/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Api/ApiKeys1Api.cs
@@ -13,7 +13,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
diff --git a/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index d0228c7e4df9..3c5feaf03db9 100644
--- a/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -53,6 +53,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -110,6 +115,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -148,6 +158,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -171,6 +182,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -182,6 +194,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 }
diff --git a/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Client/ClientUtils.cs
index 5d088a4aed4d..48719ee3a820 100644
--- a/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/latest/Tags/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -19,6 +19,7 @@
 using System.Text.Json;
 using System.Text.RegularExpressions;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -246,6 +247,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Api/DefaultApi.cs
index e3c6fb7ce136..64fe997457fc 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -245,10 +247,10 @@ public async Task<IListApiResponse> ListAsync(string personId, System.Threading.
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 2e8d3c4f3ea0..6bebfb495ae7 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index 7c70740b5f30..edb65b8265db 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -18,6 +18,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -231,6 +232,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return Enumerable.Empty<MediaTypeWithQualityHeaderValue>();
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return new [] { MediaTypeWithQualityHeaderValue.Parse("application/json") };
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs
index 0a27d3740aad..68ba3478d01e 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -219,10 +221,10 @@ public async Task<IRootGetApiResponse> RootGetAsync(System.Threading.Cancellatio
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index ce423c3672b1..6a95178fbe47 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index e58706bfa7d4..69f7ad2b7116 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -18,6 +18,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -231,6 +232,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return Enumerable.Empty<MediaTypeWithQualityHeaderValue>();
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return new [] { MediaTypeWithQualityHeaderValue.Parse("application/json") };
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Api/DefaultApi.cs
index 0a27d3740aad..68ba3478d01e 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -219,10 +221,10 @@ public async Task<IRootGetApiResponse> RootGetAsync(System.Threading.Cancellatio
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index ce423c3672b1..6a95178fbe47 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
index b15038a3fa36..217a64d7d771 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -17,6 +17,7 @@
 using System.Text.RegularExpressions;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -216,6 +217,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return Enumerable.Empty<MediaTypeWithQualityHeaderValue>();
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return new [] { MediaTypeWithQualityHeaderValue.Parse("application/json") };
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index aac86867879b..3e40f393851e 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -292,10 +294,10 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("PATCH");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/DefaultApi.cs
index 15e2eae1ae7d..d71ddb553fa8 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -527,10 +529,10 @@ public async Task<IFooGetApiResponse> FooGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -963,10 +965,10 @@ public async Task<IHelloApiResponse> HelloAsync(System.Threading.CancellationTok
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1180,10 +1182,10 @@ public async Task<IRedirectOrDefaultApiResponse> RedirectOrDefaultAsync(System.T
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1403,10 +1405,10 @@ public async Task<IRolesReportGetApiResponse> RolesReportGetAsync(System.Threadi
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1620,10 +1622,10 @@ public async Task<ITestApiResponse> TestAsync(System.Threading.CancellationToken
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
index 1d61e33426f3..cdfa43a79786 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1377,10 +1379,10 @@ public async Task<IFakeHealthGetApiResponse> FakeHealthGetAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1618,10 +1620,10 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1872,10 +1874,10 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2113,10 +2115,10 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2379,10 +2381,10 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2596,10 +2598,10 @@ public async Task<IGetArrayOfEnumsApiResponse> GetArrayOfEnumsAsync(System.Threa
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2813,10 +2815,10 @@ public async Task<IGetMixedAnyOfApiResponse> GetMixedAnyOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -3030,10 +3032,10 @@ public async Task<IGetMixedOneOfApiResponse> GetMixedOneOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -3938,10 +3940,10 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("PATCH");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index 6fa54b15e6dd..c6b04ab0ec52 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -301,10 +303,10 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("PATCH");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
index fc6b872e7d1e..018ebf57f116 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1260,10 +1262,10 @@ public async Task<IFindPetsByStatusApiResponse> FindPetsByStatusAsync(List<FindP
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1560,10 +1562,10 @@ public async Task<IFindPetsByTagsApiResponse> FindPetsByTagsAsync(List<string> t
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1812,10 +1814,10 @@ public async Task<IGetPetByIdApiResponse> GetPetByIdAsync(long petId, System.Thr
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2607,10 +2609,10 @@ public async Task<IUploadFileApiResponse> UploadFileAsync(long petId, Option<str
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2896,10 +2898,10 @@ public async Task<IUploadFileWithRequiredFileApiResponse> UploadFileWithRequired
                         "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
index d53082a6604f..8ef5b2a44f76 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -654,10 +656,10 @@ public async Task<IGetInventoryApiResponse> GetInventoryAsync(System.Threading.C
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -887,10 +889,10 @@ public async Task<IGetOrderByIdApiResponse> GetOrderByIdAsync(long orderId, Syst
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1153,10 +1155,10 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
index 31f82a00fba1..79f232b766b8 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1555,10 +1557,10 @@ public async Task<IGetUserByNameApiResponse> GetUserByNameAsync(string username,
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1869,10 +1871,10 @@ public async Task<ILoginUserApiResponse> LoginUserAsync(string password, string
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 846993850534..ed63e072b901 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
index 201f27bed522..585f78b2c231 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -18,6 +18,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -331,6 +332,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return Enumerable.Empty<MediaTypeWithQualityHeaderValue>();
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return new [] { MediaTypeWithQualityHeaderValue.Parse("application/json") };
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Api/DefaultApi.cs
index 0a27d3740aad..68ba3478d01e 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -219,10 +221,10 @@ public async Task<IRootGetApiResponse> RootGetAsync(System.Threading.Cancellatio
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index ce423c3672b1..6a95178fbe47 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index e58706bfa7d4..69f7ad2b7116 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -18,6 +18,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -231,6 +232,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return Enumerable.Empty<MediaTypeWithQualityHeaderValue>();
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return new [] { MediaTypeWithQualityHeaderValue.Parse("application/json") };
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index aac86867879b..3e40f393851e 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -292,10 +294,10 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("PATCH");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs
index 15e2eae1ae7d..d71ddb553fa8 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -527,10 +529,10 @@ public async Task<IFooGetApiResponse> FooGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -963,10 +965,10 @@ public async Task<IHelloApiResponse> HelloAsync(System.Threading.CancellationTok
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1180,10 +1182,10 @@ public async Task<IRedirectOrDefaultApiResponse> RedirectOrDefaultAsync(System.T
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1403,10 +1405,10 @@ public async Task<IRolesReportGetApiResponse> RolesReportGetAsync(System.Threadi
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1620,10 +1622,10 @@ public async Task<ITestApiResponse> TestAsync(System.Threading.CancellationToken
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
index bfa82e80ee7d..7934ed315955 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1377,10 +1379,10 @@ public async Task<IFakeHealthGetApiResponse> FakeHealthGetAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1618,10 +1620,10 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1872,10 +1874,10 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2113,10 +2115,10 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2379,10 +2381,10 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2596,10 +2598,10 @@ public async Task<IGetArrayOfEnumsApiResponse> GetArrayOfEnumsAsync(System.Threa
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2813,10 +2815,10 @@ public async Task<IGetMixedAnyOfApiResponse> GetMixedAnyOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -3030,10 +3032,10 @@ public async Task<IGetMixedOneOfApiResponse> GetMixedOneOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -3938,10 +3940,10 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("PATCH");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index 6fa54b15e6dd..c6b04ab0ec52 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -301,10 +303,10 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("PATCH");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
index 936621915c2f..7a39918bdc41 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1260,10 +1262,10 @@ public async Task<IFindPetsByStatusApiResponse> FindPetsByStatusAsync(List<strin
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1560,10 +1562,10 @@ public async Task<IFindPetsByTagsApiResponse> FindPetsByTagsAsync(List<string> t
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1812,10 +1814,10 @@ public async Task<IGetPetByIdApiResponse> GetPetByIdAsync(long petId, System.Thr
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2607,10 +2609,10 @@ public async Task<IUploadFileApiResponse> UploadFileAsync(long petId, Option<str
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2896,10 +2898,10 @@ public async Task<IUploadFileWithRequiredFileApiResponse> UploadFileWithRequired
                         "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
index d53082a6604f..8ef5b2a44f76 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -654,10 +656,10 @@ public async Task<IGetInventoryApiResponse> GetInventoryAsync(System.Threading.C
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -887,10 +889,10 @@ public async Task<IGetOrderByIdApiResponse> GetOrderByIdAsync(long orderId, Syst
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1153,10 +1155,10 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
index 31f82a00fba1..79f232b766b8 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1555,10 +1557,10 @@ public async Task<IGetUserByNameApiResponse> GetUserByNameAsync(string username,
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1869,10 +1871,10 @@ public async Task<ILoginUserApiResponse> LoginUserAsync(string password, string
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 846993850534..ed63e072b901 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 382636b9c592..c2d90fee7b00 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -18,6 +18,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -335,6 +336,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return Enumerable.Empty<MediaTypeWithQualityHeaderValue>();
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return new [] { MediaTypeWithQualityHeaderValue.Parse("application/json") };
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Api/DefaultApi.cs
index 352be5701a5f..106a89faf551 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -219,10 +221,10 @@ public async Task<INowGetApiResponse> NowGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index a5cba0e52ef5..15cf34abd897 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
index 9d704244ca60..f421f6d6c00b 100644
--- a/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -17,6 +17,7 @@
 using System.Text.RegularExpressions;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -216,6 +217,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return Enumerable.Empty<MediaTypeWithQualityHeaderValue>();
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return new [] { MediaTypeWithQualityHeaderValue.Parse("application/json") };
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Api/DefaultApi.cs
index e3c6fb7ce136..64fe997457fc 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -245,10 +247,10 @@ public async Task<IListApiResponse> ListAsync(string personId, System.Threading.
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 2e8d3c4f3ea0..6bebfb495ae7 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index 7c70740b5f30..edb65b8265db 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -18,6 +18,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -231,6 +232,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return Enumerable.Empty<MediaTypeWithQualityHeaderValue>();
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return new [] { MediaTypeWithQualityHeaderValue.Parse("application/json") };
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs
index 0a27d3740aad..68ba3478d01e 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -219,10 +221,10 @@ public async Task<IRootGetApiResponse> RootGetAsync(System.Threading.Cancellatio
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index ce423c3672b1..6a95178fbe47 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index e58706bfa7d4..69f7ad2b7116 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -18,6 +18,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -231,6 +232,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return Enumerable.Empty<MediaTypeWithQualityHeaderValue>();
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return new [] { MediaTypeWithQualityHeaderValue.Parse("application/json") };
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Api/DefaultApi.cs
index 0a27d3740aad..68ba3478d01e 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -219,10 +221,10 @@ public async Task<IRootGetApiResponse> RootGetAsync(System.Threading.Cancellatio
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index ce423c3672b1..6a95178fbe47 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
index b15038a3fa36..217a64d7d771 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -17,6 +17,7 @@
 using System.Text.RegularExpressions;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -216,6 +217,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return Enumerable.Empty<MediaTypeWithQualityHeaderValue>();
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return new [] { MediaTypeWithQualityHeaderValue.Parse("application/json") };
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index aac86867879b..3e40f393851e 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -292,10 +294,10 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("PATCH");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/DefaultApi.cs
index 15e2eae1ae7d..d71ddb553fa8 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -527,10 +529,10 @@ public async Task<IFooGetApiResponse> FooGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -963,10 +965,10 @@ public async Task<IHelloApiResponse> HelloAsync(System.Threading.CancellationTok
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1180,10 +1182,10 @@ public async Task<IRedirectOrDefaultApiResponse> RedirectOrDefaultAsync(System.T
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1403,10 +1405,10 @@ public async Task<IRolesReportGetApiResponse> RolesReportGetAsync(System.Threadi
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1620,10 +1622,10 @@ public async Task<ITestApiResponse> TestAsync(System.Threading.CancellationToken
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
index 1d61e33426f3..cdfa43a79786 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1377,10 +1379,10 @@ public async Task<IFakeHealthGetApiResponse> FakeHealthGetAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1618,10 +1620,10 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1872,10 +1874,10 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2113,10 +2115,10 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2379,10 +2381,10 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2596,10 +2598,10 @@ public async Task<IGetArrayOfEnumsApiResponse> GetArrayOfEnumsAsync(System.Threa
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2813,10 +2815,10 @@ public async Task<IGetMixedAnyOfApiResponse> GetMixedAnyOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -3030,10 +3032,10 @@ public async Task<IGetMixedOneOfApiResponse> GetMixedOneOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -3938,10 +3940,10 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("PATCH");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index 6fa54b15e6dd..c6b04ab0ec52 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -301,10 +303,10 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("PATCH");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
index fc6b872e7d1e..018ebf57f116 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1260,10 +1262,10 @@ public async Task<IFindPetsByStatusApiResponse> FindPetsByStatusAsync(List<FindP
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1560,10 +1562,10 @@ public async Task<IFindPetsByTagsApiResponse> FindPetsByTagsAsync(List<string> t
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1812,10 +1814,10 @@ public async Task<IGetPetByIdApiResponse> GetPetByIdAsync(long petId, System.Thr
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2607,10 +2609,10 @@ public async Task<IUploadFileApiResponse> UploadFileAsync(long petId, Option<str
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2896,10 +2898,10 @@ public async Task<IUploadFileWithRequiredFileApiResponse> UploadFileWithRequired
                         "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
index d53082a6604f..8ef5b2a44f76 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -654,10 +656,10 @@ public async Task<IGetInventoryApiResponse> GetInventoryAsync(System.Threading.C
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -887,10 +889,10 @@ public async Task<IGetOrderByIdApiResponse> GetOrderByIdAsync(long orderId, Syst
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1153,10 +1155,10 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
index 31f82a00fba1..79f232b766b8 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1555,10 +1557,10 @@ public async Task<IGetUserByNameApiResponse> GetUserByNameAsync(string username,
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1869,10 +1871,10 @@ public async Task<ILoginUserApiResponse> LoginUserAsync(string password, string
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 846993850534..ed63e072b901 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
index 201f27bed522..585f78b2c231 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -18,6 +18,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -331,6 +332,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return Enumerable.Empty<MediaTypeWithQualityHeaderValue>();
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return new [] { MediaTypeWithQualityHeaderValue.Parse("application/json") };
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Api/DefaultApi.cs
index 0a27d3740aad..68ba3478d01e 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -219,10 +221,10 @@ public async Task<IRootGetApiResponse> RootGetAsync(System.Threading.Cancellatio
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index ce423c3672b1..6a95178fbe47 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index e58706bfa7d4..69f7ad2b7116 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -18,6 +18,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -231,6 +232,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return Enumerable.Empty<MediaTypeWithQualityHeaderValue>();
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return new [] { MediaTypeWithQualityHeaderValue.Parse("application/json") };
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index aac86867879b..3e40f393851e 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -292,10 +294,10 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("PATCH");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs
index 15e2eae1ae7d..d71ddb553fa8 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -527,10 +529,10 @@ public async Task<IFooGetApiResponse> FooGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -963,10 +965,10 @@ public async Task<IHelloApiResponse> HelloAsync(System.Threading.CancellationTok
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1180,10 +1182,10 @@ public async Task<IRedirectOrDefaultApiResponse> RedirectOrDefaultAsync(System.T
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1403,10 +1405,10 @@ public async Task<IRolesReportGetApiResponse> RolesReportGetAsync(System.Threadi
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1620,10 +1622,10 @@ public async Task<ITestApiResponse> TestAsync(System.Threading.CancellationToken
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
index bfa82e80ee7d..7934ed315955 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1377,10 +1379,10 @@ public async Task<IFakeHealthGetApiResponse> FakeHealthGetAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1618,10 +1620,10 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1872,10 +1874,10 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2113,10 +2115,10 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2379,10 +2381,10 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2596,10 +2598,10 @@ public async Task<IGetArrayOfEnumsApiResponse> GetArrayOfEnumsAsync(System.Threa
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2813,10 +2815,10 @@ public async Task<IGetMixedAnyOfApiResponse> GetMixedAnyOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -3030,10 +3032,10 @@ public async Task<IGetMixedOneOfApiResponse> GetMixedOneOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -3938,10 +3940,10 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("PATCH");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index 6fa54b15e6dd..c6b04ab0ec52 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -301,10 +303,10 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("PATCH");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
index 936621915c2f..7a39918bdc41 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1260,10 +1262,10 @@ public async Task<IFindPetsByStatusApiResponse> FindPetsByStatusAsync(List<strin
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1560,10 +1562,10 @@ public async Task<IFindPetsByTagsApiResponse> FindPetsByTagsAsync(List<string> t
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1812,10 +1814,10 @@ public async Task<IGetPetByIdApiResponse> GetPetByIdAsync(long petId, System.Thr
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2607,10 +2609,10 @@ public async Task<IUploadFileApiResponse> UploadFileAsync(long petId, Option<str
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2896,10 +2898,10 @@ public async Task<IUploadFileWithRequiredFileApiResponse> UploadFileWithRequired
                         "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
index d53082a6604f..8ef5b2a44f76 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -654,10 +656,10 @@ public async Task<IGetInventoryApiResponse> GetInventoryAsync(System.Threading.C
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -887,10 +889,10 @@ public async Task<IGetOrderByIdApiResponse> GetOrderByIdAsync(long orderId, Syst
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1153,10 +1155,10 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
index 31f82a00fba1..79f232b766b8 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1555,10 +1557,10 @@ public async Task<IGetUserByNameApiResponse> GetUserByNameAsync(string username,
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1869,10 +1871,10 @@ public async Task<ILoginUserApiResponse> LoginUserAsync(string password, string
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 846993850534..ed63e072b901 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 382636b9c592..c2d90fee7b00 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -18,6 +18,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -335,6 +336,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return Enumerable.Empty<MediaTypeWithQualityHeaderValue>();
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return new [] { MediaTypeWithQualityHeaderValue.Parse("application/json") };
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Api/DefaultApi.cs
index 352be5701a5f..106a89faf551 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -219,10 +221,10 @@ public async Task<INowGetApiResponse> NowGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index a5cba0e52ef5..15cf34abd897 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
index 9d704244ca60..f421f6d6c00b 100644
--- a/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -17,6 +17,7 @@
 using System.Text.RegularExpressions;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -216,6 +217,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return Enumerable.Empty<MediaTypeWithQualityHeaderValue>();
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return new [] { MediaTypeWithQualityHeaderValue.Parse("application/json") };
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Api/DefaultApi.cs
index 460adaf3b6ea..1836f05b9946 100644
--- a/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -247,10 +249,10 @@ public async Task<IListApiResponse> ListAsync(string personId, System.Threading.
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index b6971b20a70b..78160f0c716c 100644
--- a/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index ea0ca69d6ace..c75a26cd1562 100644
--- a/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -20,6 +20,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -235,6 +236,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs
index 3d166af1486d..8808c802f0af 100644
--- a/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -221,10 +223,10 @@ public async Task<IRootGetApiResponse> RootGetAsync(System.Threading.Cancellatio
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 349c8a275dd2..ecf92d6ce3d9 100644
--- a/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index 2406e1ca0078..e3f39f30bec8 100644
--- a/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -20,6 +20,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -235,6 +236,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Api/DefaultApi.cs
index 3d166af1486d..8808c802f0af 100644
--- a/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -221,10 +223,10 @@ public async Task<IRootGetApiResponse> RootGetAsync(System.Threading.Cancellatio
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 349c8a275dd2..ecf92d6ce3d9 100644
--- a/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
index 0de5dc0426d7..0efabe7ad9a2 100644
--- a/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -19,6 +19,7 @@
 using System.Text.RegularExpressions;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -220,6 +221,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index a64bf2f6891b..507491eecacf 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -292,10 +294,10 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/DefaultApi.cs
index be1d170c656f..3ef2b6852935 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -527,10 +529,10 @@ public async Task<IFooGetApiResponse> FooGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -964,10 +966,10 @@ public async Task<IHelloApiResponse> HelloAsync(System.Threading.CancellationTok
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1182,10 +1184,10 @@ public async Task<IRedirectOrDefaultApiResponse> RedirectOrDefaultAsync(System.T
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1406,10 +1408,10 @@ public async Task<IRolesReportGetApiResponse> RolesReportGetAsync(System.Threadi
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1624,10 +1626,10 @@ public async Task<ITestApiResponse> TestAsync(System.Threading.CancellationToken
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
index b12a70964930..808f2c78376e 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1377,10 +1379,10 @@ public async Task<IFakeHealthGetApiResponse> FakeHealthGetAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1619,10 +1621,10 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -1874,10 +1876,10 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2116,10 +2118,10 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2383,10 +2385,10 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2601,10 +2603,10 @@ public async Task<IGetArrayOfEnumsApiResponse> GetArrayOfEnumsAsync(System.Threa
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -2819,10 +2821,10 @@ public async Task<IGetMixedAnyOfApiResponse> GetMixedAnyOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -3037,10 +3039,10 @@ public async Task<IGetMixedOneOfApiResponse> GetMixedOneOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -3946,10 +3948,10 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index 8f1e1cbae536..f549d11cfbdd 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -301,10 +303,10 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
index c7851f91380c..18c30d4185ac 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1261,10 +1263,10 @@ public async Task<IFindPetsByStatusApiResponse> FindPetsByStatusAsync(List<FindP
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1562,10 +1564,10 @@ public async Task<IFindPetsByTagsApiResponse> FindPetsByTagsAsync(List<string> t
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1815,10 +1817,10 @@ public async Task<IGetPetByIdApiResponse> GetPetByIdAsync(long petId, System.Thr
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -2611,10 +2613,10 @@ public async Task<IUploadFileApiResponse> UploadFileAsync(long petId, Option<str
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2901,10 +2903,10 @@ public async Task<IUploadFileWithRequiredFileApiResponse> UploadFileWithRequired
                         "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
index 2a5f045dc2fb..01cc491c8607 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -655,10 +657,10 @@ public async Task<IGetInventoryApiResponse> GetInventoryAsync(System.Threading.C
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -889,10 +891,10 @@ public async Task<IGetOrderByIdApiResponse> GetOrderByIdAsync(long orderId, Syst
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1156,10 +1158,10 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
index b37dc6ffc7f0..57037a1fc421 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
@@ -10,8 +10,10 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1564,10 +1566,10 @@ public async Task<IGetUserByNameApiResponse> GetUserByNameAsync(string username,
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1879,10 +1881,10 @@ public async Task<ILoginUserApiResponse> LoginUserAsync(string password, string
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index cd0c6be12fec..eb72371af4ec 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
index b7403d129fb1..97b8745cc47b 100644
--- a/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -18,6 +18,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -330,6 +331,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index 4325815a3894..cfff49d74e47 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -294,10 +296,10 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/DefaultApi.cs
index 041224a07eb0..698f0b6c57c9 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -529,10 +531,10 @@ public async Task<IFooGetApiResponse> FooGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -966,10 +968,10 @@ public async Task<IHelloApiResponse> HelloAsync(System.Threading.CancellationTok
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1184,10 +1186,10 @@ public async Task<IRedirectOrDefaultApiResponse> RedirectOrDefaultAsync(System.T
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1408,10 +1410,10 @@ public async Task<IRolesReportGetApiResponse> RolesReportGetAsync(System.Threadi
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1626,10 +1628,10 @@ public async Task<ITestApiResponse> TestAsync(System.Threading.CancellationToken
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs
index 657ea7aea6d2..354123e492f4 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1379,10 +1381,10 @@ public async Task<IFakeHealthGetApiResponse> FakeHealthGetAsync(System.Threading
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1621,10 +1623,10 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         "*/*"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -1876,10 +1878,10 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         "*/*"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2118,10 +2120,10 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         "*/*"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2385,10 +2387,10 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                         "*/*"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2603,10 +2605,10 @@ public async Task<IGetArrayOfEnumsApiResponse> GetArrayOfEnumsAsync(System.Threa
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -2821,10 +2823,10 @@ public async Task<IGetMixedAnyOfApiResponse> GetMixedAnyOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -3039,10 +3041,10 @@ public async Task<IGetMixedOneOfApiResponse> GetMixedOneOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -3948,10 +3950,10 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index f64b9b185445..e853974c29f7 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -303,10 +305,10 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs
index 86ed00cc3d0a..cef7ea20cff4 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1263,10 +1265,10 @@ public async Task<IFindPetsByStatusApiResponse> FindPetsByStatusAsync(List<strin
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1564,10 +1566,10 @@ public async Task<IFindPetsByTagsApiResponse> FindPetsByTagsAsync(List<string> t
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1817,10 +1819,10 @@ public async Task<IGetPetByIdApiResponse> GetPetByIdAsync(long petId, System.Thr
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -2613,10 +2615,10 @@ public async Task<IUploadFileApiResponse> UploadFileAsync(long petId, Option<str
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2903,10 +2905,10 @@ public async Task<IUploadFileWithRequiredFileApiResponse> UploadFileWithRequired
                         "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs
index 397183c6f558..114540a6a25a 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -657,10 +659,10 @@ public async Task<IGetInventoryApiResponse> GetInventoryAsync(System.Threading.C
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -891,10 +893,10 @@ public async Task<IGetOrderByIdApiResponse> GetOrderByIdAsync(long orderId, Syst
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1158,10 +1160,10 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs
index 0ce74696e182..f4060809ed50 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs
@@ -12,8 +12,10 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1566,10 +1568,10 @@ public async Task<IGetUserByNameApiResponse> GetUserByNameAsync(string username,
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1881,10 +1883,10 @@ public async Task<ILoginUserApiResponse> LoginUserAsync(string password, string
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 657be352a23d..8d6eb4de2804 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs
index 8a3b1e1511b2..a66181bb5473 100644
--- a/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -20,6 +20,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -336,6 +337,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Api/DefaultApi.cs
index 3d166af1486d..8808c802f0af 100644
--- a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -221,10 +223,10 @@ public async Task<IRootGetApiResponse> RootGetAsync(System.Threading.Cancellatio
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 349c8a275dd2..ecf92d6ce3d9 100644
--- a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index 2406e1ca0078..e3f39f30bec8 100644
--- a/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -20,6 +20,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -235,6 +236,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index a64bf2f6891b..507491eecacf 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -292,10 +294,10 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs
index be1d170c656f..3ef2b6852935 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -527,10 +529,10 @@ public async Task<IFooGetApiResponse> FooGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -964,10 +966,10 @@ public async Task<IHelloApiResponse> HelloAsync(System.Threading.CancellationTok
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1182,10 +1184,10 @@ public async Task<IRedirectOrDefaultApiResponse> RedirectOrDefaultAsync(System.T
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1406,10 +1408,10 @@ public async Task<IRolesReportGetApiResponse> RolesReportGetAsync(System.Threadi
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1624,10 +1626,10 @@ public async Task<ITestApiResponse> TestAsync(System.Threading.CancellationToken
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
index 76b141c8120e..88fd2f848719 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1377,10 +1379,10 @@ public async Task<IFakeHealthGetApiResponse> FakeHealthGetAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1619,10 +1621,10 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -1874,10 +1876,10 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2116,10 +2118,10 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2383,10 +2385,10 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2601,10 +2603,10 @@ public async Task<IGetArrayOfEnumsApiResponse> GetArrayOfEnumsAsync(System.Threa
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -2819,10 +2821,10 @@ public async Task<IGetMixedAnyOfApiResponse> GetMixedAnyOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -3037,10 +3039,10 @@ public async Task<IGetMixedOneOfApiResponse> GetMixedOneOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -3946,10 +3948,10 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index 8f1e1cbae536..f549d11cfbdd 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -301,10 +303,10 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
index 8cebfe5dc0ed..4442fc5d0e2f 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1261,10 +1263,10 @@ public async Task<IFindPetsByStatusApiResponse> FindPetsByStatusAsync(List<strin
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1562,10 +1564,10 @@ public async Task<IFindPetsByTagsApiResponse> FindPetsByTagsAsync(List<string> t
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1815,10 +1817,10 @@ public async Task<IGetPetByIdApiResponse> GetPetByIdAsync(long petId, System.Thr
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -2611,10 +2613,10 @@ public async Task<IUploadFileApiResponse> UploadFileAsync(long petId, Option<str
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2901,10 +2903,10 @@ public async Task<IUploadFileWithRequiredFileApiResponse> UploadFileWithRequired
                         "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
index 2a5f045dc2fb..01cc491c8607 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -655,10 +657,10 @@ public async Task<IGetInventoryApiResponse> GetInventoryAsync(System.Threading.C
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -889,10 +891,10 @@ public async Task<IGetOrderByIdApiResponse> GetOrderByIdAsync(long orderId, Syst
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1156,10 +1158,10 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
index b37dc6ffc7f0..57037a1fc421 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
@@ -10,8 +10,10 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1564,10 +1566,10 @@ public async Task<IGetUserByNameApiResponse> GetUserByNameAsync(string username,
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1879,10 +1881,10 @@ public async Task<ILoginUserApiResponse> LoginUserAsync(string password, string
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index cd0c6be12fec..eb72371af4ec 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 91be9bd4c0f8..3dfb7ecffbed 100644
--- a/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -18,6 +18,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -334,6 +335,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index 4325815a3894..cfff49d74e47 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -294,10 +296,10 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/DefaultApi.cs
index 041224a07eb0..698f0b6c57c9 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -529,10 +531,10 @@ public async Task<IFooGetApiResponse> FooGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -966,10 +968,10 @@ public async Task<IHelloApiResponse> HelloAsync(System.Threading.CancellationTok
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1184,10 +1186,10 @@ public async Task<IRedirectOrDefaultApiResponse> RedirectOrDefaultAsync(System.T
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1408,10 +1410,10 @@ public async Task<IRolesReportGetApiResponse> RolesReportGetAsync(System.Threadi
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1626,10 +1628,10 @@ public async Task<ITestApiResponse> TestAsync(System.Threading.CancellationToken
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs
index 657ea7aea6d2..354123e492f4 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1379,10 +1381,10 @@ public async Task<IFakeHealthGetApiResponse> FakeHealthGetAsync(System.Threading
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1621,10 +1623,10 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         "*/*"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -1876,10 +1878,10 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         "*/*"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2118,10 +2120,10 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         "*/*"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2385,10 +2387,10 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                         "*/*"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2603,10 +2605,10 @@ public async Task<IGetArrayOfEnumsApiResponse> GetArrayOfEnumsAsync(System.Threa
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -2821,10 +2823,10 @@ public async Task<IGetMixedAnyOfApiResponse> GetMixedAnyOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -3039,10 +3041,10 @@ public async Task<IGetMixedOneOfApiResponse> GetMixedOneOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -3948,10 +3950,10 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index f64b9b185445..e853974c29f7 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -303,10 +305,10 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs
index 86ed00cc3d0a..cef7ea20cff4 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1263,10 +1265,10 @@ public async Task<IFindPetsByStatusApiResponse> FindPetsByStatusAsync(List<strin
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1564,10 +1566,10 @@ public async Task<IFindPetsByTagsApiResponse> FindPetsByTagsAsync(List<string> t
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1817,10 +1819,10 @@ public async Task<IGetPetByIdApiResponse> GetPetByIdAsync(long petId, System.Thr
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -2613,10 +2615,10 @@ public async Task<IUploadFileApiResponse> UploadFileAsync(long petId, Option<str
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2903,10 +2905,10 @@ public async Task<IUploadFileWithRequiredFileApiResponse> UploadFileWithRequired
                         "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs
index 397183c6f558..114540a6a25a 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -657,10 +659,10 @@ public async Task<IGetInventoryApiResponse> GetInventoryAsync(System.Threading.C
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -891,10 +893,10 @@ public async Task<IGetOrderByIdApiResponse> GetOrderByIdAsync(long orderId, Syst
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1158,10 +1160,10 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs
index 0ce74696e182..f4060809ed50 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs
@@ -12,8 +12,10 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1566,10 +1568,10 @@ public async Task<IGetUserByNameApiResponse> GetUserByNameAsync(string username,
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1881,10 +1883,10 @@ public async Task<ILoginUserApiResponse> LoginUserAsync(string password, string
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 657be352a23d..8d6eb4de2804 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs
index 8a3b1e1511b2..a66181bb5473 100644
--- a/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -20,6 +20,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -336,6 +337,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Api/DefaultApi.cs
index 610a3704b124..adaf287f4aa7 100644
--- a/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -221,10 +223,10 @@ public async Task<INowGetApiResponse> NowGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index e64afdb6bee7..344e2255924b 100644
--- a/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
index 7f26eb170ddc..55d79ce4b6a8 100644
--- a/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net8/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -19,6 +19,7 @@
 using System.Text.RegularExpressions;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -220,6 +221,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Api/DefaultApi.cs
index 460adaf3b6ea..1836f05b9946 100644
--- a/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -247,10 +249,10 @@ public async Task<IListApiResponse> ListAsync(string personId, System.Threading.
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index b6971b20a70b..78160f0c716c 100644
--- a/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index ea0ca69d6ace..c75a26cd1562 100644
--- a/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AllOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -20,6 +20,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -235,6 +236,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs
index 3d166af1486d..8808c802f0af 100644
--- a/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -221,10 +223,10 @@ public async Task<IRootGetApiResponse> RootGetAsync(System.Threading.Cancellatio
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 349c8a275dd2..ecf92d6ce3d9 100644
--- a/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index 2406e1ca0078..e3f39f30bec8 100644
--- a/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AnyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -20,6 +20,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -235,6 +236,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Api/DefaultApi.cs
index 3d166af1486d..8808c802f0af 100644
--- a/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -221,10 +223,10 @@ public async Task<IRootGetApiResponse> RootGetAsync(System.Threading.Cancellatio
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 349c8a275dd2..ecf92d6ce3d9 100644
--- a/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
index 0de5dc0426d7..0efabe7ad9a2 100644
--- a/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/AnyOfNoCompare/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -19,6 +19,7 @@
 using System.Text.RegularExpressions;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -220,6 +221,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index a64bf2f6891b..507491eecacf 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -292,10 +294,10 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/DefaultApi.cs
index be1d170c656f..3ef2b6852935 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -527,10 +529,10 @@ public async Task<IFooGetApiResponse> FooGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -964,10 +966,10 @@ public async Task<IHelloApiResponse> HelloAsync(System.Threading.CancellationTok
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1182,10 +1184,10 @@ public async Task<IRedirectOrDefaultApiResponse> RedirectOrDefaultAsync(System.T
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1406,10 +1408,10 @@ public async Task<IRolesReportGetApiResponse> RolesReportGetAsync(System.Threadi
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1624,10 +1626,10 @@ public async Task<ITestApiResponse> TestAsync(System.Threading.CancellationToken
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
index b12a70964930..808f2c78376e 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1377,10 +1379,10 @@ public async Task<IFakeHealthGetApiResponse> FakeHealthGetAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1619,10 +1621,10 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -1874,10 +1876,10 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2116,10 +2118,10 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2383,10 +2385,10 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2601,10 +2603,10 @@ public async Task<IGetArrayOfEnumsApiResponse> GetArrayOfEnumsAsync(System.Threa
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -2819,10 +2821,10 @@ public async Task<IGetMixedAnyOfApiResponse> GetMixedAnyOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -3037,10 +3039,10 @@ public async Task<IGetMixedOneOfApiResponse> GetMixedOneOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -3946,10 +3948,10 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index 8f1e1cbae536..f549d11cfbdd 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -301,10 +303,10 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
index c7851f91380c..18c30d4185ac 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/PetApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1261,10 +1263,10 @@ public async Task<IFindPetsByStatusApiResponse> FindPetsByStatusAsync(List<FindP
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1562,10 +1564,10 @@ public async Task<IFindPetsByTagsApiResponse> FindPetsByTagsAsync(List<string> t
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1815,10 +1817,10 @@ public async Task<IGetPetByIdApiResponse> GetPetByIdAsync(long petId, System.Thr
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -2611,10 +2613,10 @@ public async Task<IUploadFileApiResponse> UploadFileAsync(long petId, Option<str
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2901,10 +2903,10 @@ public async Task<IUploadFileWithRequiredFileApiResponse> UploadFileWithRequired
                         "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
index 2a5f045dc2fb..01cc491c8607 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -655,10 +657,10 @@ public async Task<IGetInventoryApiResponse> GetInventoryAsync(System.Threading.C
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -889,10 +891,10 @@ public async Task<IGetOrderByIdApiResponse> GetOrderByIdAsync(long orderId, Syst
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1156,10 +1158,10 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
index b37dc6ffc7f0..57037a1fc421 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Api/UserApi.cs
@@ -10,8 +10,10 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1564,10 +1566,10 @@ public async Task<IGetUserByNameApiResponse> GetUserByNameAsync(string username,
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1879,10 +1881,10 @@ public async Task<ILoginUserApiResponse> LoginUserAsync(string password, string
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index cd0c6be12fec..eb72371af4ec 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
index b7403d129fb1..97b8745cc47b 100644
--- a/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/FormModels/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -18,6 +18,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -330,6 +331,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index 4325815a3894..cfff49d74e47 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -294,10 +296,10 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/DefaultApi.cs
index 041224a07eb0..698f0b6c57c9 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -529,10 +531,10 @@ public async Task<IFooGetApiResponse> FooGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -966,10 +968,10 @@ public async Task<IHelloApiResponse> HelloAsync(System.Threading.CancellationTok
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1184,10 +1186,10 @@ public async Task<IRedirectOrDefaultApiResponse> RedirectOrDefaultAsync(System.T
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1408,10 +1410,10 @@ public async Task<IRolesReportGetApiResponse> RolesReportGetAsync(System.Threadi
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1626,10 +1628,10 @@ public async Task<ITestApiResponse> TestAsync(System.Threading.CancellationToken
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs
index 657ea7aea6d2..354123e492f4 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1379,10 +1381,10 @@ public async Task<IFakeHealthGetApiResponse> FakeHealthGetAsync(System.Threading
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1621,10 +1623,10 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         "*/*"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -1876,10 +1878,10 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         "*/*"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2118,10 +2120,10 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         "*/*"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2385,10 +2387,10 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                         "*/*"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2603,10 +2605,10 @@ public async Task<IGetArrayOfEnumsApiResponse> GetArrayOfEnumsAsync(System.Threa
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -2821,10 +2823,10 @@ public async Task<IGetMixedAnyOfApiResponse> GetMixedAnyOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -3039,10 +3041,10 @@ public async Task<IGetMixedOneOfApiResponse> GetMixedOneOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -3948,10 +3950,10 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index f64b9b185445..e853974c29f7 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -303,10 +305,10 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs
index 86ed00cc3d0a..cef7ea20cff4 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/PetApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1263,10 +1265,10 @@ public async Task<IFindPetsByStatusApiResponse> FindPetsByStatusAsync(List<strin
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1564,10 +1566,10 @@ public async Task<IFindPetsByTagsApiResponse> FindPetsByTagsAsync(List<string> t
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1817,10 +1819,10 @@ public async Task<IGetPetByIdApiResponse> GetPetByIdAsync(long petId, System.Thr
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -2613,10 +2615,10 @@ public async Task<IUploadFileApiResponse> UploadFileAsync(long petId, Option<str
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2903,10 +2905,10 @@ public async Task<IUploadFileWithRequiredFileApiResponse> UploadFileWithRequired
                         "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs
index 397183c6f558..114540a6a25a 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -657,10 +659,10 @@ public async Task<IGetInventoryApiResponse> GetInventoryAsync(System.Threading.C
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -891,10 +893,10 @@ public async Task<IGetOrderByIdApiResponse> GetOrderByIdAsync(long orderId, Syst
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1158,10 +1160,10 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs
index 0ce74696e182..f4060809ed50 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Api/UserApi.cs
@@ -12,8 +12,10 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1566,10 +1568,10 @@ public async Task<IGetUserByNameApiResponse> GetUserByNameAsync(string username,
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1881,10 +1883,10 @@ public async Task<ILoginUserApiResponse> LoginUserAsync(string password, string
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 657be352a23d..8d6eb4de2804 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs
index 8a3b1e1511b2..a66181bb5473 100644
--- a/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/NullReferenceTypes/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -20,6 +20,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -336,6 +337,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Api/DefaultApi.cs
index 3d166af1486d..8808c802f0af 100644
--- a/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -221,10 +223,10 @@ public async Task<IRootGetApiResponse> RootGetAsync(System.Threading.Cancellatio
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 349c8a275dd2..ecf92d6ce3d9 100644
--- a/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index 2406e1ca0078..e3f39f30bec8 100644
--- a/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/OneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -20,6 +20,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -235,6 +236,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index a64bf2f6891b..507491eecacf 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -292,10 +294,10 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs
index be1d170c656f..3ef2b6852935 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -527,10 +529,10 @@ public async Task<IFooGetApiResponse> FooGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -964,10 +966,10 @@ public async Task<IHelloApiResponse> HelloAsync(System.Threading.CancellationTok
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1182,10 +1184,10 @@ public async Task<IRedirectOrDefaultApiResponse> RedirectOrDefaultAsync(System.T
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1406,10 +1408,10 @@ public async Task<IRolesReportGetApiResponse> RolesReportGetAsync(System.Threadi
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1624,10 +1626,10 @@ public async Task<ITestApiResponse> TestAsync(System.Threading.CancellationToken
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
index 76b141c8120e..88fd2f848719 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1377,10 +1379,10 @@ public async Task<IFakeHealthGetApiResponse> FakeHealthGetAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1619,10 +1621,10 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -1874,10 +1876,10 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2116,10 +2118,10 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2383,10 +2385,10 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2601,10 +2603,10 @@ public async Task<IGetArrayOfEnumsApiResponse> GetArrayOfEnumsAsync(System.Threa
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -2819,10 +2821,10 @@ public async Task<IGetMixedAnyOfApiResponse> GetMixedAnyOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -3037,10 +3039,10 @@ public async Task<IGetMixedOneOfApiResponse> GetMixedOneOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -3946,10 +3948,10 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index 8f1e1cbae536..f549d11cfbdd 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -301,10 +303,10 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
index 8cebfe5dc0ed..4442fc5d0e2f 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1261,10 +1263,10 @@ public async Task<IFindPetsByStatusApiResponse> FindPetsByStatusAsync(List<strin
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1562,10 +1564,10 @@ public async Task<IFindPetsByTagsApiResponse> FindPetsByTagsAsync(List<string> t
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1815,10 +1817,10 @@ public async Task<IGetPetByIdApiResponse> GetPetByIdAsync(long petId, System.Thr
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -2611,10 +2613,10 @@ public async Task<IUploadFileApiResponse> UploadFileAsync(long petId, Option<str
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2901,10 +2903,10 @@ public async Task<IUploadFileWithRequiredFileApiResponse> UploadFileWithRequired
                         "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
index 2a5f045dc2fb..01cc491c8607 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -655,10 +657,10 @@ public async Task<IGetInventoryApiResponse> GetInventoryAsync(System.Threading.C
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -889,10 +891,10 @@ public async Task<IGetOrderByIdApiResponse> GetOrderByIdAsync(long orderId, Syst
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1156,10 +1158,10 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
index b37dc6ffc7f0..57037a1fc421 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
@@ -10,8 +10,10 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1564,10 +1566,10 @@ public async Task<IGetUserByNameApiResponse> GetUserByNameAsync(string username,
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1879,10 +1881,10 @@ public async Task<ILoginUserApiResponse> LoginUserAsync(string password, string
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index cd0c6be12fec..eb72371af4ec 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -50,6 +50,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -107,6 +112,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -145,6 +155,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -168,6 +179,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -179,6 +191,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 91be9bd4c0f8..3dfb7ecffbed 100644
--- a/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -18,6 +18,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -334,6 +335,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index 4325815a3894..cfff49d74e47 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -294,10 +296,10 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/DefaultApi.cs
index 041224a07eb0..698f0b6c57c9 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -529,10 +531,10 @@ public async Task<IFooGetApiResponse> FooGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -966,10 +968,10 @@ public async Task<IHelloApiResponse> HelloAsync(System.Threading.CancellationTok
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1184,10 +1186,10 @@ public async Task<IRedirectOrDefaultApiResponse> RedirectOrDefaultAsync(System.T
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1408,10 +1410,10 @@ public async Task<IRolesReportGetApiResponse> RolesReportGetAsync(System.Threadi
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1626,10 +1628,10 @@ public async Task<ITestApiResponse> TestAsync(System.Threading.CancellationToken
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs
index 657ea7aea6d2..354123e492f4 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1379,10 +1381,10 @@ public async Task<IFakeHealthGetApiResponse> FakeHealthGetAsync(System.Threading
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1621,10 +1623,10 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         "*/*"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -1876,10 +1878,10 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         "*/*"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2118,10 +2120,10 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         "*/*"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2385,10 +2387,10 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                         "*/*"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2603,10 +2605,10 @@ public async Task<IGetArrayOfEnumsApiResponse> GetArrayOfEnumsAsync(System.Threa
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -2821,10 +2823,10 @@ public async Task<IGetMixedAnyOfApiResponse> GetMixedAnyOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -3039,10 +3041,10 @@ public async Task<IGetMixedOneOfApiResponse> GetMixedOneOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -3948,10 +3950,10 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index f64b9b185445..e853974c29f7 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -303,10 +305,10 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Patch;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs
index 86ed00cc3d0a..cef7ea20cff4 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/PetApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1263,10 +1265,10 @@ public async Task<IFindPetsByStatusApiResponse> FindPetsByStatusAsync(List<strin
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1564,10 +1566,10 @@ public async Task<IFindPetsByTagsApiResponse> FindPetsByTagsAsync(List<string> t
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1817,10 +1819,10 @@ public async Task<IGetPetByIdApiResponse> GetPetByIdAsync(long petId, System.Thr
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -2613,10 +2615,10 @@ public async Task<IUploadFileApiResponse> UploadFileAsync(long petId, Option<str
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
@@ -2903,10 +2905,10 @@ public async Task<IUploadFileWithRequiredFileApiResponse> UploadFileWithRequired
                         "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs
index 397183c6f558..114540a6a25a 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -657,10 +659,10 @@ public async Task<IGetInventoryApiResponse> GetInventoryAsync(System.Threading.C
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -891,10 +893,10 @@ public async Task<IGetOrderByIdApiResponse> GetOrderByIdAsync(long orderId, Syst
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1158,10 +1160,10 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Post;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs
index 0ce74696e182..f4060809ed50 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Api/UserApi.cs
@@ -12,8 +12,10 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1566,10 +1568,10 @@ public async Task<IGetUserByNameApiResponse> GetUserByNameAsync(string username,
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
@@ -1881,10 +1883,10 @@ public async Task<ILoginUserApiResponse> LoginUserAsync(string password, string
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 657be352a23d..8d6eb4de2804 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs
index 8a3b1e1511b2..a66181bb5473 100644
--- a/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/SourceGeneration/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -20,6 +20,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -336,6 +337,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Api/DefaultApi.cs
index 610a3704b124..adaf287f4aa7 100644
--- a/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -12,7 +12,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -221,10 +223,10 @@ public async Task<INowGetApiResponse> NowGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string? acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
 
                     httpRequestMessageLocalVar.Method = HttpMethod.Get;
 
diff --git a/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index e64afdb6bee7..344e2255924b 100644
--- a/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -52,6 +52,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -109,6 +114,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -147,6 +157,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -170,6 +181,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -181,6 +193,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
index 7f26eb170ddc..55d79ce4b6a8 100644
--- a/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/net9/UseDateTimeForDate/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -19,6 +19,7 @@
 using System.Text.RegularExpressions;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -220,6 +221,26 @@ public static byte[] ReadAsBytes(Stream inputStream)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return [];
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return [MediaTypeWithQualityHeaderValue.Parse("application/json")];
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
index 169b9470ad4b..389fd63ab339 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -291,10 +293,10 @@ public async Task<ICall123TestSpecialTagsApiResponse> Call123TestSpecialTagsAsyn
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("PATCH");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs
index 5ca198780cd7..d3e371440177 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/DefaultApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -526,10 +528,10 @@ public async Task<IFooGetApiResponse> FooGetAsync(System.Threading.CancellationT
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -962,10 +964,10 @@ public async Task<IHelloApiResponse> HelloAsync(System.Threading.CancellationTok
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1179,10 +1181,10 @@ public async Task<IRedirectOrDefaultApiResponse> RedirectOrDefaultAsync(System.T
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1402,10 +1404,10 @@ public async Task<IRolesReportGetApiResponse> RolesReportGetAsync(System.Threadi
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1619,10 +1621,10 @@ public async Task<ITestApiResponse> TestAsync(System.Threading.CancellationToken
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
index dbfc7ba00f4c..7110fb455c32 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/FakeApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1376,10 +1378,10 @@ public async Task<IFakeHealthGetApiResponse> FakeHealthGetAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1617,10 +1619,10 @@ public async Task<IFakeOuterBooleanSerializeApiResponse> FakeOuterBooleanSeriali
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1871,10 +1873,10 @@ public async Task<IFakeOuterCompositeSerializeApiResponse> FakeOuterCompositeSer
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2112,10 +2114,10 @@ public async Task<IFakeOuterNumberSerializeApiResponse> FakeOuterNumberSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2378,10 +2380,10 @@ public async Task<IFakeOuterStringSerializeApiResponse> FakeOuterStringSerialize
                         "*/*"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2595,10 +2597,10 @@ public async Task<IGetArrayOfEnumsApiResponse> GetArrayOfEnumsAsync(System.Threa
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2812,10 +2814,10 @@ public async Task<IGetMixedAnyOfApiResponse> GetMixedAnyOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -3029,10 +3031,10 @@ public async Task<IGetMixedOneOfApiResponse> GetMixedOneOfAsync(System.Threading
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -3937,10 +3939,10 @@ public async Task<ITestClientModelApiResponse> TestClientModelAsync(ModelClient
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("PATCH");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
index 7c4fa9b1483e..1fcd03e08daf 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/FakeClassnameTags123Api.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -300,10 +302,10 @@ public async Task<ITestClassnameApiResponse> TestClassnameAsync(ModelClient mode
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("PATCH");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/PetApi.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
index 18f2ab3e6509..de479ed63dfb 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/PetApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1259,10 +1261,10 @@ public async Task<IFindPetsByStatusApiResponse> FindPetsByStatusAsync(List<strin
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1559,10 +1561,10 @@ public async Task<IFindPetsByTagsApiResponse> FindPetsByTagsAsync(List<string> t
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1811,10 +1813,10 @@ public async Task<IGetPetByIdApiResponse> GetPetByIdAsync(long petId, System.Thr
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2606,10 +2608,10 @@ public async Task<IUploadFileApiResponse> UploadFileAsync(long petId, Option<str
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -2895,10 +2897,10 @@ public async Task<IUploadFileWithRequiredFileApiResponse> UploadFileWithRequired
                         "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
index cb016f72f98c..a10d2f6a10e3 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/StoreApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -653,10 +655,10 @@ public async Task<IGetInventoryApiResponse> GetInventoryAsync(System.Threading.C
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -886,10 +888,10 @@ public async Task<IGetOrderByIdApiResponse> GetOrderByIdAsync(long orderId, Syst
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1152,10 +1154,10 @@ public async Task<IPlaceOrderApiResponse> PlaceOrderAsync(Order order, System.Th
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("POST");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/UserApi.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
index 6e0a6dc77415..69c6ea454abe 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Api/UserApi.cs
@@ -10,7 +10,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Net;
+using System.IO;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using System.Net.Http;
@@ -1554,10 +1556,10 @@ public async Task<IGetUserByNameApiResponse> GetUserByNameAsync(string username,
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
@@ -1868,10 +1870,10 @@ public async Task<ILoginUserApiResponse> LoginUserAsync(string password, string
                         "application/json"
                     };
 
-                    string acceptLocalVar = ClientUtils.SelectHeaderAccept(acceptLocalVars);
+                    IEnumerable<MediaTypeWithQualityHeaderValue> acceptHeaderValuesLocalVar = ClientUtils.SelectHeaderAcceptArray(acceptLocalVars);
 
-                    if (acceptLocalVar != null)
-                        httpRequestMessageLocalVar.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(acceptLocalVar));
+                    foreach (var acceptLocalVar in acceptHeaderValuesLocalVar)
+                        httpRequestMessageLocalVar.Headers.Accept.Add(acceptLocalVar);
                     httpRequestMessageLocalVar.Method = new HttpMethod("GET");
 
                     DateTime requestedAtLocalVar = DateTime.UtcNow;
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs
index 918f5ba89d32..f6a1ddbe6b26 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Client/ApiResponse`1.cs
@@ -49,6 +49,11 @@ public partial interface IApiResponse
         /// </summary>
         System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The path used when making the request.
         /// </summary>
@@ -106,6 +111,11 @@ public partial class ApiResponse : IApiResponse
         /// </summary>
         public System.Net.Http.Headers.HttpResponseHeaders Headers { get; }
 
+        /// <summary>
+        /// The headers contained in the api response related to the content
+        /// </summary>
+        public System.Net.Http.Headers.HttpContentHeaders ContentHeaders { get; }
+
         /// <summary>
         /// The DateTime when the request was retrieved.
         /// </summary>
@@ -144,6 +154,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             RawContent = rawContent;
@@ -167,6 +178,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
         {
             StatusCode = httpResponseMessage.StatusCode;
             Headers = httpResponseMessage.Headers;
+            ContentHeaders = httpResponseMessage.Content.Headers;
             IsSuccessStatusCode = httpResponseMessage.IsSuccessStatusCode;
             ReasonPhrase = httpResponseMessage.ReasonPhrase;
             ContentStream = contentStream;
@@ -178,6 +190,7 @@ public ApiResponse(global::System.Net.Http.HttpRequestMessage httpRequestMessage
             OnCreated(httpRequestMessage, httpResponseMessage);
         }
 
+
         partial void OnCreated(global::System.Net.Http.HttpRequestMessage httpRequestMessage, System.Net.Http.HttpResponseMessage httpResponseMessage);
     }
 
diff --git a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 382636b9c592..c2d90fee7b00 100644
--- a/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/generichost/standard2.0/Petstore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -18,6 +18,7 @@
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
 using System.Runtime.CompilerServices;
+using System.Net.Http.Headers;
 
 [assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
@@ -335,6 +336,26 @@ public static string SelectHeaderAccept(string[] accepts)
             return string.Join(",", accepts);
         }
 
+        
+
+        /// <summary>
+        /// Select the Accept header's value from the given accepts array:
+        /// if JSON exists in the given array, use it;
+        /// otherwise use all of them.
+        /// </summary>
+        /// <param name="accepts">The accepts array to select from.</param>
+        /// <returns>The Accept header values to use.</returns>
+        public static IEnumerable<MediaTypeWithQualityHeaderValue> SelectHeaderAcceptArray(string[] accepts)
+        {
+            if (accepts.Length == 0)
+                    return Enumerable.Empty<MediaTypeWithQualityHeaderValue>();
+
+            if (accepts.Contains("application/json", StringComparer.OrdinalIgnoreCase))
+                    return new [] { MediaTypeWithQualityHeaderValue.Parse("application/json") };
+
+            return accepts.Select(MediaTypeWithQualityHeaderValue.Parse);
+        }
+
         /// <summary>
         /// Provides a case-insensitive check that a provided content type is a known JSON-like content type.
         /// </summary>