Fix CarouselView ItemTemplate Runtime Updates (#29546)

* Fixed the item template dynamic changes

* Added a test case

* Added test case and added snapshots

* committed the image

* committed the image

Author: Shalini-Ashokan

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

@@ -87,6 +87,7 @@ protected override void UpdateItemTemplate()
 				return;
 
 			ListViewBase.ItemTemplate = CarouselItemsViewTemplate;
+			UpdateItemsSource();
 		}
 
 		protected override void OnScrollViewerFound(ScrollViewer scrollViewer)

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

@@ -0,0 +1,98 @@
+using System.Collections.ObjectModel;
+
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 29462, "CarouselView ItemTemplate Not Updating at Runtime", PlatformAffected.UWP)]
+public class Issue29462 : ContentPage
+{
+	public Issue29462()
+	{
+		var verticalStackLayout = new VerticalStackLayout();
+		var carouselItems = new ObservableCollection<string>
+		{
+			"Item 0",
+			"Item 1",
+			"Item 2",
+			"Item 3",
+			"Item 4",
+		};
+
+		CarouselView2 carouselView = new CarouselView2
+		{
+			ItemsSource = carouselItems,
+			ItemsUpdatingScrollMode = ItemsUpdatingScrollMode.KeepScrollOffset,
+			HeightRequest = 300,
+			Loop = false,
+			HorizontalScrollBarVisibility = ScrollBarVisibility.Never,
+			ItemTemplate = new DataTemplate(() =>
+			{
+				var grid = new Grid
+				{
+					Padding = 10
+				};
+
+				var label = new Label
+				{
+					VerticalOptions = LayoutOptions.Center,
+					HorizontalOptions = LayoutOptions.Center,
+					FontSize = 18,
+				};
+				label.SetBinding(Label.TextProperty, ".");
+				label.SetBinding(Label.AutomationIdProperty, ".");
+
+				grid.Children.Add(label);
+				return grid;
+			}),
+			HorizontalOptions = LayoutOptions.Fill,
+		};
+
+		var indicatorView = new IndicatorView
+		{
+			HorizontalOptions = LayoutOptions.Center,
+			VerticalOptions = LayoutOptions.Center
+		};
+		carouselView.IndicatorView = indicatorView;
+
+		var itemTempateButton = new Button
+		{
+			Text = "Change Item Template",
+			AutomationId = "ChangeItemTemplate",
+			Margin = new Thickness(20),
+		};
+
+		itemTempateButton.Clicked += (sender, e) =>
+		{
+			carouselView.ItemTemplate = new DataTemplate(() =>
+			{
+				Grid grid = new Grid
+				{
+					BackgroundColor = Colors.LightGray,
+					HeightRequest = 200,
+					WidthRequest = 300,
+					Margin = new Thickness(10)
+				};
+
+				var label = new Label
+				{
+					HorizontalOptions = LayoutOptions.Center,
+					VerticalOptions = LayoutOptions.Center,
+					FontSize = 24,
+					TextColor = Colors.DarkBlue
+				};
+
+				label.SetBinding(Label.TextProperty, new Binding(".")
+				{
+					StringFormat = "{0} (Grid Template)"
+				});
+
+				grid.Children.Add(label);
+				return grid;
+			});
+		};
+
+		verticalStackLayout.Children.Add(carouselView);
+		verticalStackLayout.Children.Add(indicatorView);
+		verticalStackLayout.Children.Add(itemTempateButton);
+		Content = verticalStackLayout;
+	}
+}

src/Controls/tests/TestCases.HostApp/Issues/Issue29462.cs

@@ -0,0 +1,23 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue29462 : _IssuesUITest
+{
+	public override string Issue => "CarouselView ItemTemplate Not Updating at Runtime";
+
+	public Issue29462(TestDevice device)
+	: base(device)
+	{ }
+
+	[Test]
+	[Category(UITestCategories.CarouselView)]
+	public void TestDynamicItemTemplateChangeInCarouselView()
+	{
+		App.WaitForElement("ChangeItemTemplate");
+		App.Tap("ChangeItemTemplate");
+		VerifyScreenshot();
+	}
+}