Resolve some compilation warnings

Author: MichaelGrafnetter

.editorconfig

@@ -72,6 +72,8 @@ dotnet_naming_symbols.constant_fields.required_modifiers          = const
 ###############################
 # CA1051: Do not declare visible instance fields
 dotnet_code_quality.ca1051.api_surface = public
+# CA1819: Properties should not return arrays (suppressed due to heavy interop code use)
+dotnet_diagnostic.CA1819.severity = none
 ###############################
 # C# Coding Conventions       #
 ###############################

Src/DSInternals.Win32.WebAuthn.Adapter.Tests/WebAuthnApiAdapterTester.cs

@@ -181,7 +181,7 @@ public void WebAuthN_GetAssertion_Cancel()
 
             var webauthn = new WebAuthnApiAdapter();
 
-            var source = new CancellationTokenSource(5000); // Cancel in 5 seconds
+            using var source = new CancellationTokenSource(5000); // Cancel in 5 seconds
             Assert.ThrowsExactly<OperationCanceledException>(() =>
                 webauthn.AuthenticatorGetAssertionAsync(options, null, source.Token).GetAwaiter().GetResult());
         }

Src/DSInternals.Win32.WebAuthn/Cryptography/X509CertificateLoaderPolyfill.cs

@@ -0,0 +1,22 @@
+#if !NET9_0_OR_GREATER
+using System;
+
+namespace System.Security.Cryptography.X509Certificates;
+
+/// <summary>
+/// Provides compatibility members for APIs added to newer .NET versions.
+/// </summary>
+public static class X509CertificateLoader
+{
+    /// <summary>
+    /// Loads an X.509 certificate from raw DER/BER encoded bytes.
+    /// </summary>
+    /// <param name="data">The raw certificate bytes.</param>
+    /// <returns>The loaded certificate.</returns>
+    public static X509Certificate2 LoadCertificate(byte[] data)
+    {
+        ArgumentNullException.ThrowIfNull(data);
+        return new X509Certificate2(data);
+    }
+}
+#endif

Src/DSInternals.Win32.WebAuthn/Interop/Marshalers/AuthenticatorDetailsListSafeHandle.cs

@@ -13,7 +13,7 @@ protected override bool ReleaseHandle()
         return true;
     }
 
-    internal AuthenticatorDetailsOut[] ToManaged()
+    internal AuthenticatorDetailsOut[]? ToManaged()
     {
         if (this.IsInvalid)
         {

Src/DSInternals.Win32.WebAuthn/Interop/Marshalers/ByteArray.cs

@@ -7,7 +7,7 @@ namespace DSInternals.Win32.WebAuthn.Interop
     [StructLayout(LayoutKind.Sequential)]
     internal class ByteArrayOut
     {
-        protected IntPtr _nativeArray = IntPtr.Zero;
+        protected IntPtr _nativeArray;
 
         // This class is only created by marshaling.
         protected ByteArrayOut() { }

Src/DSInternals.Win32.WebAuthn/Interop/Marshalers/CredentialAttestationSafeHandle.cs

@@ -15,7 +15,7 @@ protected override bool ReleaseHandle()
             return true;
         }
 
-        internal CredentialAttestation ToManaged()
+        internal CredentialAttestation? ToManaged()
         {
             if (this.IsInvalid)
             {

Src/DSInternals.Win32.WebAuthn/Interop/Marshalers/PlatformCredentialListSafeHandle.cs

@@ -14,7 +14,7 @@ protected override bool ReleaseHandle()
             return true;
         }
 
-        internal CredentialDetailsOut[] ToManaged()
+        internal CredentialDetailsOut[]? ToManaged()
         {
             return Marshal.PtrToStructure<CredentialDetailsList>(handle)?.Items;
         }

Src/DSInternals.Win32.WebAuthn/Interop/Marshalers/SafeStringArray.cs

@@ -7,7 +7,7 @@ namespace DSInternals.Win32.WebAuthn.Interop
     internal class SafeStringArrayIn : IDisposable
     {
         protected int _length;
-        protected IntPtr _nativeArray = IntPtr.Zero;
+        protected IntPtr _nativeArray;
 
         public SafeStringArrayIn(string[]? items)
         {

Src/DSInternals.Win32.WebAuthn/Interop/Marshalers/SafeStructArray.cs

@@ -7,7 +7,7 @@ namespace DSInternals.Win32.WebAuthn.Interop
     internal abstract class SafeStructArrayOut<T>
     {
         protected int _length;
-        protected IntPtr _nativeArray = IntPtr.Zero;
+        protected IntPtr _nativeArray;
 
         protected SafeStructArrayOut()
         {
@@ -42,7 +42,7 @@ public T[]? Items
     internal abstract class SafeStructArrayIn<T> : IDisposable
     {
         protected int _length;
-        protected IntPtr _nativeArray = IntPtr.Zero;
+        protected IntPtr _nativeArray;
 
         public SafeStructArrayIn(T[]? items)
         {

Src/DSInternals.Win32.WebAuthn/Interop/Marshalers/VersionedStructMarshaler.cs

@@ -5,17 +5,14 @@ namespace DSInternals.Win32.WebAuthn.Interop
 {
     internal static class VersionedStructMarshaler
     {
-        public static T PtrToStructure<T>(IntPtr ptr, int sourceStructSize) where T : class
+        public static T? PtrToStructure<T>(IntPtr ptr, int sourceStructSize) where T : class
         {
             if (ptr == IntPtr.Zero || sourceStructSize == 0)
             {
                 return null;
             }
 
-            if (sourceStructSize < 0)
-            {
-                throw new ArgumentOutOfRangeException(nameof(sourceStructSize));
-            }
+            ArgumentOutOfRangeException.ThrowIfNegative(sourceStructSize);
 
             int targetStructSize = Marshal.SizeOf<T>();