[Windows] Fix for Assigning null to the SelectedItem of the CollectionView in the SelectionChanged event does not clear the selection (#29288)

* Fix for 10025 (Setting the CollectionView's SelectedItem to null on selection changed event does nothing)

* Have added the test case

* Have added the snapshots

Author: SyedAbdulAzeemSF4852

src/Controls/src/Core/Handlers/Items/SelectableItemsViewHandler.Windows.cs

@@ -14,6 +14,7 @@ namespace Microsoft.Maui.Controls.Handlers.Items
 	public partial class SelectableItemsViewHandler<TItemsView> : StructuredItemsViewHandler<TItemsView> where TItemsView : SelectableItemsView
 	{
 		bool _ignorePlatformSelectionChange;
+		bool _ignoreVirtualSelectionChange;
 
 		protected override void ConnectHandler(ListViewBase platformView)
 		{
@@ -132,6 +133,13 @@ void UpdatePlatformSelection()
 
 		void VirtualSelectionChanged(object sender, SelectionChangedEventArgs e)
 		{
+			// When the selection changes within the SelectionChanged event, the new selection isn't immediately reflected in the view.
+			// After the virtual selection is correctly updated, the flag is reset to enable future updates
+			if (_ignoreVirtualSelectionChange)
+			{
+				_ignoreVirtualSelectionChange = false;
+				return;
+			}
 			UpdatePlatformSelection();
 		}
 
@@ -172,10 +180,10 @@ void UpdateVirtualSingleSelection()
 
 			if (ItemsView != null)
 			{
-				ItemsView.SelectionChanged -= VirtualSelectionChanged;
+				_ignoreVirtualSelectionChange = true;
 				ItemsView.SelectedItem = selectedItem;
 
-				ItemsView.SelectionChanged += VirtualSelectionChanged;
+				_ignoreVirtualSelectionChange = false;
 			}
 		}
 

src/Controls/tests/TestCases.Android.Tests/snapshots/android/VerifySelectedItemClearsOnNullAssignment.png

@@ -0,0 +1,48 @@
+namespace Controls.TestCases.HostApp.Issues;
+
+[Issue(IssueTracker.Github, 10025, "Assigning null to the SelectedItem of the CollectionView in the SelectionChanged event does not clear the selection as expected", PlatformAffected.UWP)]
+public class Issue10025 : ContentPage
+{
+	CollectionView collectionView;
+	public Issue10025()
+	{
+		Label descriptionLabel = new Label
+		{
+			AutomationId = "DescriptionLabel",
+			Text = "The test passes if the SelectedItem is set to null and no visual selection indicator is displayed; otherwise, it fails",
+			Margin = new Thickness(10),
+		};
+
+		collectionView = new CollectionView
+		{
+			SelectionMode = SelectionMode.Single,
+			ItemsSource = new List<string> { "Item1", "Item2" },
+			ItemTemplate = new DataTemplate(() =>
+			{
+				Label label = new Label();
+
+				label.SetBinding(Label.TextProperty, ".");
+				label.SetBinding(Label.AutomationIdProperty, ".");
+
+				return label;
+			})
+		};
+
+		collectionView.SelectionChanged += SelectionChangedEvent;
+
+		Content = new VerticalStackLayout
+		{
+			Padding = new Thickness(20),
+			Children =
+			{
+				descriptionLabel,
+				collectionView
+			}
+		};
+	}
+
+	private void SelectionChangedEvent(object sender, SelectionChangedEventArgs e)
+	{
+		collectionView.SelectedItem = null;
+	}
+}

src/Controls/tests/TestCases.HostApp/Issues/Issue10025.cs

@@ -0,0 +1,25 @@
+#if TEST_FAILS_ON_IOS && TEST_FAILS_ON_CATALYST // Select items traces are preserved Issue Link - https://github.com/dotnet/maui/issues/26187
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue10025 : _IssuesUITest
+{
+	public Issue10025(TestDevice device) : base(device)
+	{
+	}
+
+	public override string Issue => "Assigning null to the SelectedItem of the CollectionView in the SelectionChanged event does not clear the selection as expected";
+
+	[Test]
+	[Category(UITestCategories.CollectionView)]
+	public void VerifySelectedItemClearsOnNullAssignment()
+	{
+		App.Tap("Item1");
+		App.Tap("DescriptionLabel");
+		VerifyScreenshot();
+	}
+}
+#endif