Added improvement to automation peer to throw ElementNotEnabledException if attempting to update value when in a readonly state

Author: jamesmcroft

Microsoft.Toolkit.Uwp.UI.Controls.Input/TokenizingTextBox/TokenizingTextBoxAutomationPeer.cs

@@ -45,8 +45,14 @@ private TokenizingTextBox OwningTokenizingTextBox
 
         /// <summary>Sets the value of a control.</summary>
         /// <param name="value">The value to set. The provider is responsible for converting the value to the appropriate data type.</param>
+        /// <exception cref="T:Windows.UI.Xaml.Automation.ElementNotEnabledException">Thrown if the control is in a read-only state.</exception>
         public void SetValue(string value)
         {
+            if (IsReadOnly)
+            {
+                throw new ElementNotEnabledException($"Could not set the value of the {nameof(TokenizingTextBox)} ");
+            }
+
             this.OwningTokenizingTextBox.Text = value;
         }
 

UnitTests/UnitTests.UWP/UI/Controls/Test_TokenizingTextBox_AutomationPeer.cs

@@ -45,11 +45,32 @@ await App.DispatcherQueue.EnqueueAsync(async () =>
                 tokenizingTextBox.Name = expectedName;
                 Assert.IsTrue(tokenizingTextBoxAutomationPeer.GetName().Contains(expectedName), "Verify that the UIA name contains the given Name of the TokenizingTextBox.");
 
-                tokenizingTextBox.Text = expectedValue;
+                tokenizingTextBoxAutomationPeer.SetValue(expectedValue);
                 Assert.IsTrue(tokenizingTextBoxAutomationPeer.Value.Equals(expectedValue), "Verify that the Value contains the given Text of the TokenizingTextBox.");
             });
         }
 
+        [TestMethod]
+        public async Task ShouldThrowElementNotEnabledExceptionIfValueSetWhenDisabled()
+        {
+            await App.DispatcherQueue.EnqueueAsync(async () =>
+            {
+                const string expectedValue = "Wor";
+
+                var tokenizingTextBox = new TokenizingTextBox { IsEnabled = false };
+
+                await SetTestContentAsync(tokenizingTextBox);
+
+                var tokenizingTextBoxAutomationPeer =
+                    FrameworkElementAutomationPeer.CreatePeerForElement(tokenizingTextBox) as TokenizingTextBoxAutomationPeer;
+
+                Assert.ThrowsException<ElementNotEnabledException>(() =>
+                {
+                    tokenizingTextBoxAutomationPeer.SetValue(expectedValue);
+                });
+            });
+        }
+
         public class TokenizingTextBoxTestItem
         {
             public string Title { get; set; }