[Windows] Fixed Shell flyout background image does not displayed

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

@@ -42,6 +42,7 @@ private void OnLoaded(object sender, UI.Xaml.RoutedEventArgs e)
 		{
 			UpdateValue(nameof(Shell.FlyoutIcon));
 			UpdateValue(nameof(Shell.FlyoutBackground));
+			UpdateValue(nameof(Shell.FlyoutBackgroundImage));
 		}
 
 		protected override void DisconnectHandler(ShellView platformView)
@@ -93,6 +94,7 @@ void OnPaneOpening(UI.Xaml.Controls.NavigationView sender, object args)
 		{
 			UpdateValue(nameof(Shell.FlyoutBackground));
 			UpdateValue(nameof(Shell.FlyoutVerticalScrollMode));
+			UpdateValue(nameof(Shell.FlyoutBackgroundImage));
 			PlatformView.UpdateFlyoutBackdrop();
 			PlatformView.UpdateFlyoutPosition();
 			VirtualView.FlyoutIsPresented = true;
@@ -127,6 +129,16 @@ public static void MapFlyoutBackground(ShellHandler handler, Shell view)
 					view.FlyoutBackgroundColor?.AsPaint());
 		}
 
+		//TODO: Make it public in .NET 10.
+		internal static void MapFlyoutBackgroundImage(ShellHandler handler, Shell view)
+		{
+			var provider = handler.GetRequiredService<IImageSourceServiceProvider>();
+			if (handler?.PlatformView is not null && provider is not null)
+			{
+				handler.PlatformView.UpdateBackgroundImageSourceAsync(view.FlyoutBackgroundImage, provider, view.FlyoutBackgroundImageAspect).FireAndForget();
+			}
+		}
+
 		public static void MapFlyoutIcon(ShellHandler handler, Shell view)
 		{
 			var flyoutIcon = view.FlyoutIcon;

src/Controls/src/Core/Handlers/Shell/ShellHandler.cs

@@ -35,6 +35,8 @@ public partial class ShellHandler
 					[nameof(Shell.FlyoutIcon)] = MapFlyoutIcon,
 					[nameof(Shell.FlyoutContentTemplate)] = MapFlyout,
 					[nameof(Shell.FlowDirection)] = MapFlowDirection,
+					[nameof(Shell.FlyoutBackgroundImage)] = MapFlyoutBackgroundImage,
+					[nameof(Shell.FlyoutBackgroundImageAspect)] = MapFlyoutBackgroundImage,
 #endif
 				};
 

src/Controls/tests/TestCases.HostApp/Issues/Issue21472.cs

@@ -0,0 +1,50 @@
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 21472, "Shell FlyoutBackgroundImage doesn't shown", PlatformAffected.UWP)]
+public class Issue21472 : TestShell
+{
+	protected override void Init()
+	{
+		var page = new ContentPage();
+		this.BindingContext = this;
+
+		FlyoutBackgroundImage = "dotnet_bot.png";
+		AddFlyoutItem(page, "Flyout Item");
+
+		var button = new Button
+		{
+			Text = "RemoveFlyoutBackground",
+			HorizontalOptions = LayoutOptions.Center,
+			VerticalOptions = LayoutOptions.Center,
+			AutomationId = "button"
+		};
+
+		button.Clicked += (sender, e) =>
+		{
+			Shell.Current.FlyoutBackgroundImage = null;
+		};
+
+		page.Content = button;
+
+		FlyoutContentTemplate = new DataTemplate(() =>
+		{
+			var stackLayout = new StackLayout();
+
+			var closeButton = new Button
+			{
+				Text = "Close Flyout",
+				AutomationId = "CloseFlyoutButton",
+				Margin = new Thickness(20),
+				HorizontalOptions = LayoutOptions.Center
+			};
+
+			closeButton.Clicked += (sender, e) =>
+			{
+				Shell.Current.FlyoutIsPresented = false;
+			};
+
+			stackLayout.Add(closeButton);
+			return stackLayout;
+		});
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue21472.cs

@@ -0,0 +1,33 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+public class Issue21472 : _IssuesUITest
+{
+	public Issue21472(TestDevice testDevice) : base(testDevice)
+	{
+	}
+	public override string Issue => "Shell FlyoutBackgroundImage doesn't shown";
+
+	[Test, Order(1)]
+	[Category(UITestCategories.Shell)]
+	public void VerifyShellFlyoutBackgroundImage()
+	{
+		App.WaitForElement("button");
+		App.ShowFlyout();
+		App.WaitForElement("CloseFlyoutButton");
+		VerifyScreenshot();
+		App.Tap("CloseFlyoutButton");
+	}
+
+	[Test, Order(2)]
+	[Category(UITestCategories.Shell)]
+	public void VerifyShellFlyoutBackgroundImageSetNull()
+	{
+		App.WaitForElement("button");
+		App.Tap("button");
+		App.ShowFlyout();
+		VerifyScreenshot();
+	}
+}

src/Core/src/Platform/Windows/NavigationViewExtensions.cs

@@ -256,6 +256,42 @@ public static void UpdateFlyoutWidth(this MauiNavigationView navigationView, IFl
 			//handler.PlatformView.OpenPaneLength = handler.PlatformView.TemplateSettings.OpenPaneWidth;
 		}
 
+		internal static async Task UpdateBackgroundImageSourceAsync(this MauiNavigationView navigationView, IImageSource? imageSource, IImageSourceServiceProvider? provider, Aspect aspect)
+		{
+			if (provider is null || imageSource is null)
+			{
+				return;
+			}
+			var paneContentGrid = navigationView.PaneContentGrid;
+			if (paneContentGrid is null)
+			{
+				return;
+			}
+
+			var service = provider.GetRequiredImageSourceService(imageSource);
+			var nativeImageSource = await service.GetImageSourceAsync(imageSource);
+
+			if (nativeImageSource is null)
+			{
+				paneContentGrid.Background = null;
+				return;
+			}
+
+			var BackgroundImage = new ImageBrush
+			{
+				ImageSource = nativeImageSource?.Value,
+				Stretch = aspect switch
+				{
+					Aspect.AspectFit => Stretch.Uniform,
+					Aspect.AspectFill => Stretch.UniformToFill,
+					Aspect.Fill => Stretch.Fill,
+					_ => Stretch.None
+				}
+			};
+
+			paneContentGrid.Background = BackgroundImage;
+		}
+
 		public static async Task UpdateFlyoutIconAsync(this MauiNavigationView navigationView, IImageSource? imageSource, IImageSourceServiceProvider? provider)
 		{
 			var togglePaneButton = navigationView.TogglePaneButton;