Merge pull request #3960 from RosarioPulella/unsetValue-to-null

Fix Incorrect usages of UnsetValue

Author: michael-hawker

Microsoft.Toolkit.Uwp.SampleApp/SamplePages/EnumValuesExtension/AnimalToColorConverter.xaml.cs

@@ -5,6 +5,7 @@
 using System;
 using Microsoft.Toolkit.Uwp.SampleApp.Enums;
 using Windows.UI;
+using Windows.UI.Xaml;
 using Windows.UI.Xaml.Data;
 
 namespace Microsoft.Toolkit.Uwp.SampleApp.Converters
@@ -21,7 +22,7 @@ public object Convert(object value, Type targetType, object parameter, string la
                 Animal.Llama => Colors.Beige,
                 Animal.Parrot => Colors.YellowGreen,
                 Animal.Squirrel => Colors.SaddleBrown,
-                _ => throw new ArgumentException("Invalid value", nameof(value))
+                _ => DependencyProperty.UnsetValue
             };
         }
 

Microsoft.Toolkit.Uwp.SampleApp/SamplePages/EnumValuesExtension/EnumValuesExtensionCode.bind

@@ -20,7 +20,7 @@ public sealed class AnimalToColorConverter : IValueConverter
             Animal.Bunny => Colors.Green,
             Animal.Parrot => Colors.YellowGreen,
             Animal.Squirrel => Colors.SaddleBrown,
-            _ => throw new ArgumentException("Invalid value", nameof(value))
+            _ => DependencyProperty.UnsetValue
         };
     }
 

Microsoft.Toolkit.Uwp.UI/Converters/TaskResultConverter.cs

@@ -4,6 +4,7 @@
 
 using System;
 using System.Threading.Tasks;
+using Windows.UI.Xaml;
 using Windows.UI.Xaml.Data;
 
 namespace Microsoft.Toolkit.Uwp.UI.Converters
@@ -26,7 +27,7 @@ public object Convert(object value, Type targetType, object parameter, string la
                 return task.GetResultOrDefault();
             }
 
-            return null;
+            return DependencyProperty.UnsetValue;
         }
 
         /// <inheritdoc/>

Microsoft.Toolkit.Uwp.UI/Extensions/UIElementExtensions.cs

@@ -20,7 +20,7 @@ public static class UIElementExtensions
             "ClipToBounds",
             typeof(bool),
             typeof(UIElementExtensions),
-            new PropertyMetadata(DependencyProperty.UnsetValue, OnClipToBoundsPropertyChanged));
+            new PropertyMetadata(null, OnClipToBoundsPropertyChanged));
 
         /// <summary>
         /// Gets the value of <see cref="ClipToBoundsProperty"/>

UnitTests/UnitTests.UWP/Converters/Test_TaskResultConverter.cs

@@ -8,6 +8,7 @@
 using Microsoft.Toolkit.Uwp.UI.Converters;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Microsoft.VisualStudio.TestTools.UnitTesting.AppContainer;
+using Windows.UI.Xaml;
 
 namespace UnitTests.Converters
 {
@@ -70,12 +71,19 @@ public void Test_TaskResultConverter_Instance_String()
 
         [TestCategory("Converters")]
         [UITestMethod]
-        public void Test_TaskResultConverter_Instance_Null()
+        public void Test_TaskResultConverter_Instance_UnsetValue()
         {
             var converter = new TaskResultConverter();
 
-            Assert.AreEqual(null, converter.Convert(null, null, null, null));
-            Assert.AreEqual(null, converter.Convert("Hello world", null, null, null));
+            Assert.AreEqual(DependencyProperty.UnsetValue, converter.Convert(null, null, null, null));
+            Assert.AreEqual(DependencyProperty.UnsetValue, converter.Convert("Hello world", null, null, null));
+         }
+
+        [TestCategory("Converters")]
+        [UITestMethod]
+        public void Test_TaskResultConverter_Instance_Null()
+        {
+            var converter = new TaskResultConverter();
 
             var cts = new CancellationTokenSource();