[Windows] - Fix for Shell Section Visibility changes not reflected un…

…til Tab switch (dotnet#26130)

* Shell section visibility fix.

* Added test case.

* Windows ShellSectionHandler changes.

* Windows test script changes

* snapshot for Windows

src/Controls/src/Core/Handlers/Shell/ShellItemHandler.Windows.cs

@@ -151,7 +151,7 @@ private void OnNavigationTabChanged(NavigationView sender, NavigationViewSelecti
 			}
 		}
 
-		void MapMenuItems()
+		internal void MapMenuItems()
 		{
 			IShellItemController shellItemController = VirtualView;
 			var items = new List<BaseShellItem>();

src/Controls/src/Core/Handlers/Shell/ShellSectionHandler.Windows.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Collections.Specialized;
 using System.Text;
 using Microsoft.Maui.Controls.Internals;
 using WFrame = Microsoft.UI.Xaml.Controls.Frame;
@@ -54,6 +55,8 @@ public override void SetVirtualView(Maui.IElement view)
 			{
 				((IShellSectionController)_shellSection).NavigationRequested -= OnNavigationRequested;
 
+				((IShellSectionController)_shellSection).ItemsCollectionChanged -= OnItemsCollectionChanged;
+
 				if (_lastShell?.Target is IShellController shell)
 				{
 					shell.RemoveAppearanceObserver(this);
@@ -82,6 +85,8 @@ public override void SetVirtualView(Maui.IElement view)
 			{
 				((IShellSectionController)_shellSection).NavigationRequested += OnNavigationRequested;
 
+				((IShellSectionController)_shellSection).ItemsCollectionChanged += OnItemsCollectionChanged;
+
 				var shell = _shellSection.FindParentOfType<Shell>() as IShellController;
 				if (shell != null)
 				{
@@ -96,6 +101,17 @@ void OnNavigationRequested(object? sender, NavigationRequestedEventArgs e)
 			SyncNavigationStack(e.Animated, e);
 		}
 
+		void OnItemsCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
+		{
+			if (_shellSection is null)
+				return;
+
+			if (_shellSection.Parent is ShellItem shellItem && shellItem.Handler is ShellItemHandler shellItemHandler)
+			{
+				shellItemHandler.MapMenuItems();
+			}
+		}
+
 		void SyncNavigationStack(bool animated, NavigationRequestedEventArgs? e)
 		{
 			// Current Item might transition to null while visibility is adjusting on shell

src/Controls/tests/TestCases.HostApp/Issues/Issue25913.cs

@@ -0,0 +1,99 @@
+namespace Maui.Controls.Sample.Issues
+{
+	[Issue(IssueTracker.Github, 25913, "Top Tab Visibility Changes Not Reflected Until Tab Switch", PlatformAffected.UWP)]
+	public partial class Issue25913 : Shell
+	{
+		public Issue25913()
+		{
+			InitializeShell();
+		}
+
+		private void InitializeShell()
+		{
+			var tabBar = new TabBar();
+
+			var tab1 = new Tab { Title = "Tab 1" };
+			var topTab1Content = new ContentPage
+			{
+				Title = "TopTab1",
+				Content = CreateControlPanel()
+			};
+
+			var topTab2Content = new ContentPage
+			{
+				Title = "TopTab2",
+				Content = CreateControlPanel()
+			};
+
+			var topTab3Content = new ContentPage
+			{
+				Title = "TopTab3",
+				Content = CreateControlPanel()
+			};
+
+			tab1.Items.Add(topTab1Content);
+			tab1.Items.Add(topTab2Content);
+			tab1.Items.Add(topTab3Content);
+
+			var tab2 = new Tab
+			{
+				Title = "Tab 2",
+				Items =
+				{
+					new ShellContent
+					{
+						Content = new ContentPage
+						{
+							Content = new Label { Text = "Tab 2 Content" }
+						}
+					}
+				}
+			};
+
+			var tab3 = new Tab
+			{
+				Title = "Tab 3",
+				Items =
+				{
+					new ShellContent
+					{
+						Content = new ContentPage
+						{
+							Content = new Label { Text = "Tab 3 Content" }
+						}
+					}
+				}
+			};
+
+			tabBar.Items.Add(tab1);
+			tabBar.Items.Add(tab2);
+			tabBar.Items.Add(tab3);
+
+			Items.Add(tabBar);
+		}
+
+		private View CreateControlPanel()
+		{
+			return new ScrollView
+			{
+				Content = new StackLayout
+				{
+					Spacing = 10,
+					Padding = new Thickness(20),
+					Children =
+					{
+						new Button
+						{
+							Text = "Hide Top Tab 3",
+							Command = new Command(() =>
+							{
+								Items[0].Items[0].Items[2].IsVisible = false;
+							}),
+							AutomationId = "HideTop3"
+						}
+					}
+				}
+			};
+		}
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue25913.cs

@@ -0,0 +1,27 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+	public class Issue25913 : _IssuesUITest
+	{
+		public override string Issue => "Top Tab Visibility Changes Not Reflected Until Tab Switch";
+
+		public Issue25913(TestDevice device)
+		: base(device)
+		{ }
+
+		[Test]
+		[Category(UITestCategories.Shell)]
+		public void DynamicTabSectionVisibility()
+		{
+			App.WaitForElement("HideTop3");
+			App.Tap("HideTop3");
+#if WINDOWS
+			App.Tap("Tab 1");
+#endif
+			VerifyScreenshot();
+		}
+	}
+}