Fix issue with InputValidationAdorner not resolving once validation error has been fixed by user

Refactored logic into RefreshErrors method to be also used if INotifyDataErrorInfo context or property is dynamically changed as well.

Author: michael-hawker

components/Adorners/src/InputValidation/InputValidationAdorner.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Collections;
 using System.ComponentModel.DataAnnotations;
 
 using INotifyDataErrorInfo = System.ComponentModel.INotifyDataErrorInfo;
@@ -29,7 +30,7 @@ public string PropertyName
     /// Identifies the <see cref="PropertyName"/> dependency property.
     /// </summary>
     public static readonly DependencyProperty PropertyNameProperty =
-        DependencyProperty.Register(nameof(PropertyName), typeof(string), typeof(InputValidationAdorner), new PropertyMetadata(null));
+        DependencyProperty.Register(nameof(PropertyName), typeof(string), typeof(InputValidationAdorner), new PropertyMetadata(null, (s, e) => (s as InputValidationAdorner)?.RefreshErrors()));
 
     /// <summary>
     /// Gets or sets the <see cref="INotifyDataErrorInfo"/> context object to use for validation.
@@ -44,7 +45,7 @@ public INotifyDataErrorInfo NotifyDataErrorInfo
     /// Identifies the <see cref="NotifyDataErrorInfo"/> dependency property.
     /// </summary>
     public static readonly DependencyProperty NotifyDataErrorInfoProperty =
-        DependencyProperty.Register(nameof(NotifyDataErrorInfo), typeof(INotifyDataErrorInfo), typeof(InputValidationAdorner), new PropertyMetadata(null));
+        DependencyProperty.Register(nameof(NotifyDataErrorInfo), typeof(INotifyDataErrorInfo), typeof(InputValidationAdorner), new PropertyMetadata(null, (s, e) => (s as InputValidationAdorner)?.RefreshErrors()));
 
     /// <summary>
     /// Gets or sets whether the validation adorners is displayed (handled automatically).
@@ -76,6 +77,8 @@ public string ValidationMessage
     public static readonly DependencyProperty ValidationMessageProperty =
         DependencyProperty.Register(nameof(ValidationMessage), typeof(string), typeof(InputValidationAdorner), new PropertyMetadata(null));
 
+    // TODO: Do we consider an InfoBar style Severity property?
+
     /// <summary>
     /// Initializes a new instance of the <see cref="InputValidationAdorner"/> class.
     /// </summary>
@@ -103,45 +106,47 @@ protected override void OnAttached()
 
     private void INotifyDataErrorInfo_ErrorsChanged(object? sender, DataErrorsChangedEventArgs e)
     {
-        if (NotifyDataErrorInfo is not null)
-        {
-            // Reset state
-            if (!NotifyDataErrorInfo.HasErrors)
-            {
-                HasValidationFailed = false;
-                ValidationMessage = string.Empty;
-                return;
-            }
+        RefreshErrors();
+    }
 
-            if (e.PropertyName == PropertyName)
+    private void RefreshErrors()
+    {
+        // Check if we have any errors for our specified property
+        if (NotifyDataErrorInfo is not null
+            && PropertyName is not null
+            && NotifyDataErrorInfo.GetErrors(PropertyName) is IEnumerable errors
+            && errors.Cast<object>().Any())
+        {
+            // Build up error messages depending on error collection type.
+            StringBuilder message = new();
+            if (errors is IEnumerable<ValidationResult> validationResults)
             {
-                HasValidationFailed = true;
-
-                var errors = NotifyDataErrorInfo.GetErrors(e.PropertyName);
-
-                StringBuilder message = new();
-                if (errors is IEnumerable<ValidationResult> validationResults)
+                foreach (ValidationResult result in validationResults)
                 {
-                    foreach (ValidationResult result in validationResults)
-                    {
-                        message.AppendLine(result.ErrorMessage);
-                    }
+                    message.AppendLine(result.ErrorMessage);
                 }
-                else if (errors is IEnumerable<string> stringErrors)
+            }
+            else if (errors is IEnumerable<string> stringErrors)
+            {
+                foreach (string result in stringErrors)
                 {
-                    foreach (string result in stringErrors)
-                    {
-                        message.AppendLine(result);
-                    }
+                    message.AppendLine(result);
                 }
-                else
-                {
-                    // TODO: Not sure if should handle more types of collections here?
-                    throw new ArgumentException("The errors returned by INotifyDataErrorInfo.GetErrors must be of type IEnumerable<ValidationResult> or IEnumerable<string>.");
-                }                
-
-                ValidationMessage = message.ToString().Trim();
             }
+            else
+            {
+                // TODO: Not sure if should handle more types of collections here?
+                throw new ArgumentException("The errors returned by INotifyDataErrorInfo.GetErrors must be of type IEnumerable<ValidationResult> or IEnumerable<string>.");
+            }
+
+            HasValidationFailed = true;
+            ValidationMessage = message.ToString().Trim();
+        }
+        else
+        {
+            // Hide if we have no object or errors to validate against.
+            HasValidationFailed = false;
+            ValidationMessage = string.Empty;
         }
     }