Fix for Shell does not always raise Navigating event on Windows (#28315)

* Fix Changes and testcases

* Update ShellItemHandler.Windows.cs

* commit for label changes

* Update ShellItemHandler.Windows.cs

Author: SuthiYuvaraj

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

@@ -169,9 +169,15 @@ private void OnNavigationTabChanged(NavigationView sender, NavigationViewSelecti
 
 				((Shell)VirtualView.Parent).CurrentItem = shellSection;
 			}
-			else if (selectedItem.Data is ShellContent shellContent)
+			else if (selectedItem.Data is ShellContent shellContent && VirtualView.Parent is Shell parentShell)
 			{
-				((Shell)VirtualView.Parent).CurrentItem = shellContent;
+				// We need to invoke ProposeSection for TabBar items navigation for ShellContent
+				var currentItem = parentShell.CurrentItem?.CurrentItem;
+				if (currentItem?.Title != shellContent.Title && currentItem != shellContent.Parent)
+				{
+					(parentShell.CurrentItem as IShellItemController)?.ProposeSection(shellContent);
+				}
+				parentShell.CurrentItem = shellContent;
 			}
 		}
 

src/Controls/tests/TestCases.HostApp/Issues/Issue12500.cs

@@ -0,0 +1,113 @@
+using System.ComponentModel;
+using Maui.Controls.Sample.Issues;
+using Microsoft.Maui;
+using Microsoft.Maui.Controls;
+
+namespace Controls.TestCases.Issues;
+
+[Issue(IssueTracker.Github, 12500, "Shell does not always raise Navigating event on Windows", PlatformAffected.UWP)]
+public class Issue12500 : Shell
+{
+	private NavigationViewModel _viewModel;
+	public Issue12500()
+	{
+		this.FlyoutBehavior = FlyoutBehavior.Disabled;
+
+		_viewModel = new NavigationViewModel();
+
+		// Create TabBar
+		var tabBar = new TabBar();
+
+		// Add ShellContent for MainPage
+		tabBar.Items.Add(new ShellContent
+		{
+			Title = "Hello, World!",
+			Route = "MainPage",
+			ContentTemplate = new DataTemplate(() => new Issue12500Main { BindingContext = _viewModel })
+		});
+		// Add ShellContent for EventsPage
+		tabBar.Items.Add(new ShellContent
+		{
+			Title = "Events",
+			Route = "EventPage",
+			ContentTemplate = new DataTemplate(() => new Issue12500EventPage { BindingContext = _viewModel })
+		});
+
+		// Add TabBar to Shell
+		this.Items.Add(tabBar);
+	}
+	protected override void OnNavigating(ShellNavigatingEventArgs args)
+	{
+		base.OnNavigating(args);
+		string targetPageRoute = args.Target.Location.ToString();
+
+		// Update ViewModel with new navigation text
+		_viewModel.LabelText = $"Navigating to {targetPageRoute}";
+
+	}
+}
+public class Issue12500EventPage : ContentPage
+{
+	public Issue12500EventPage()
+	{
+		var label = new Label
+		{
+			AutomationId = "Issue12500EventPage",
+			FontSize = 24,
+			HorizontalOptions = LayoutOptions.Center,
+			VerticalOptions = LayoutOptions.Center
+		};
+		label.SetBinding(Label.TextProperty, nameof(NavigationViewModel.LabelText)); // Bind to ViewModel
+
+		Content = new VerticalStackLayout
+		{
+			Children = { label }
+		};
+	}
+}
+
+public class Issue12500Main : ContentPage
+{
+	public Issue12500Main()
+	{
+		var label = new Label
+		{
+			AutomationId = "Issue12500MainPage",
+			FontSize = 24,
+			HorizontalOptions = LayoutOptions.Center,
+			VerticalOptions = LayoutOptions.Center
+		};
+		label.SetBinding(Label.TextProperty, nameof(NavigationViewModel.LabelText)); // Bind to ViewModel
+
+		Content = new VerticalStackLayout
+		{
+			Children = { label }
+		};
+	}
+}
+
+
+public class NavigationViewModel : INotifyPropertyChanged
+{
+	private string _labelText;
+
+	public string LabelText
+	{
+		get => _labelText;
+		set
+		{
+			if (_labelText != value)
+			{
+				_labelText = value;
+				OnPropertyChanged(nameof(LabelText));
+			}
+		}
+	}
+
+	public event PropertyChangedEventHandler PropertyChanged;
+
+	protected virtual void OnPropertyChanged(string propertyName)
+	{
+		PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue12500.cs

@@ -0,0 +1,25 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue12500 : _IssuesUITest
+{
+	public override string Issue => "Shell does not always raise Navigating event on Windows";
+
+	public Issue12500(TestDevice device) : base(device)
+	{
+	}
+
+	[Test]
+	[Category(UITestCategories.Shell)]
+	public void ShellNavigatingShouldTrigger()
+	{
+		App.WaitForElement("Issue12500MainPage");
+		App.WaitForElement("Events");
+		App.Tap("Events");
+		var result = App.WaitForElement("Issue12500EventPage").GetText();
+		Assert.That(result, Is.EqualTo("Navigating to //EventPage"));
+	}
+}