Make XAML Source Generator (XSG) the default inflator for .NET 11

Directory.Build.props

@@ -2,16 +2,6 @@
   <Import Project="Sdk.props" Sdk="Microsoft.DotNet.Arcade.Sdk" />
   <Import Condition="'$(EnvironmentBuildPropsImported)' != 'True'" Project="$(MSBuildThisFileDirectory)eng\Environment.Build.props" />
 
-  <PropertyGroup>
-    <!-- 
-      Keep backward compatibility with XamlC, XamlCompilationAttribute, and xaml-comp processing instruction
-      When we're ready to turn this off, we can remove all code depending on this condition, and drop this property group
-      -->
-
-    <_MauiXamlSourceGenBackCompat>true</_MauiXamlSourceGenBackCompat>
-    <DefineConstants Condition=" '$(_MauiXamlSourceGenBackCompat)' == 'true' ">$(DefineConstants);_MAUIXAML_SOURCEGEN_BACKCOMPAT</DefineConstants>
-  </PropertyGroup>
-
   <PropertyGroup>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <!-- Detailed trimmer warnings, if present -->

docs/design/FeatureSwitches.md

@@ -6,6 +6,7 @@ The following switches are toggled for applications running on Mono for `TrimMod
 
 | MSBuild Property Name | AppContext Setting | Description |
 |-|-|-|
+| MauiXamlInflator | N/A | Controls how XAML files are processed. See [XAML Inflator](#mauixamlinflator) section below. |
 | MauiEnableIVisualAssemblyScanning | Microsoft.Maui.RuntimeFeature.IsIVisualAssemblyScanningEnabled | When enabled, MAUI will scan assemblies for types implementing `IVisual` and for `[assembly: Visual(...)]` attributes and register these types. |
 | MauiShellSearchResultsRendererDisplayMemberNameSupported | Microsoft.Maui.RuntimeFeature.IsShellSearchResultsRendererDisplayMemberNameSupported | When disabled, it is necessary to always set `ItemTemplate` of any `SearchHandler`. Displaying search results through `DisplayMemberName` will not work. |
 | MauiQueryPropertyAttributeSupport | Microsoft.Maui.RuntimeFeature.IsQueryPropertyAttributeSupported | When disabled, the `[QueryProperty(...)]` attributes won't be used to set values to properties when navigating. |
@@ -18,6 +19,41 @@ The following switches are toggled for applications running on Mono for `TrimMod
 | EnableMauiDiagnostics | Microsoft.Maui.RuntimeFeature.EnableMauiDiagnostics | Enables MAUI specific diagnostics, like VisualDiagnostics and BindingDiagnostics. Defaults to EnableDiagnostics |
 | _EnableMauiAspire | Microsoft.Maui.RuntimeFeature.EnableMauiAspire | When enabled, MAUI Aspire integration features are available. **Warning**: Using Aspire outside of Debug configuration may introduce performance and security risks in production. |
 
+## MauiXamlInflator
+
+Controls how XAML files are processed and compiled. Starting with .NET 11, the default value is `SourceGen`.
+
+**Available Values:**
+- `SourceGen` (default) - XAML is compiled to C# at build time using a source generator. This provides the best performance and debugging experience, including full XAML Hot Reload support.
+- `Runtime` - XAML is inflated at runtime. This has negative performance impact and is deprecated.
+- `XamlC` - XAML is compiled using the XamlC IL weaver after compilation. This prevents some debugging capabilities like XAML Hot Reload and is deprecated.
+
+**Example:**
+```xml
+<PropertyGroup>
+  <!-- Use default (SourceGen) - recommended -->
+  <!-- No need to specify MauiXamlInflator -->
+
+  <!-- Or explicitly set deprecated inflators (will produce warning MAUI1001) -->
+  <MauiXamlInflator>Runtime</MauiXamlInflator>
+</PropertyGroup>
+```
+
+**Per-file override:**
+You can override the inflator for individual XAML files using item metadata:
+```xml
+<ItemGroup>
+  <MauiXaml Update="MyPage.xaml" Inflator="Runtime" />
+</ItemGroup>
+```
+
+**Changes in .NET 11:**
+- The default inflator changed from configuration-based (Runtime in Debug, XamlC in Release) to `SourceGen` for all configurations.
+- The `[XamlCompilation]` attribute is deprecated (produces warning) but still functional.
+
+**Changes in .NET 12:**
+- The `[XamlCompilation]` attribute will be obsolete with `error: true` and becomes a no-op. Use MSBuild properties or item metadata instead.
+
 ## MauiEnableIVisualAssemblyScanning
 
 When this feature is not enabled, custom and third party `IVisual` types will not be automatically discovered and registered.

src/Controls/samples/Controls.Sample.Embedding/Maui.Controls.Sample.Embedding.csproj

@@ -10,6 +10,8 @@
     <Nullable>enable</Nullable>
     <MauiEnablePlatformUsings>true</MauiEnablePlatformUsings>
     <NoWarn>$(NoWarn);XC0022</NoWarn>
+    <!-- This sample has nullability mismatches - use Runtime inflation -->
+    <MauiXamlInflator>Runtime</MauiXamlInflator>
 
     <!-- Display name -->
     <ApplicationTitle>.NET MAUI Embedding</ApplicationTitle>

src/Controls/samples/Controls.Sample.Profiling/Maui.Controls.Sample.Profiling.csproj

@@ -12,6 +12,8 @@
     <IsPackable>false</IsPackable>
     <EmitCompilerGeneratedFiles Condition="'$(Configuration)' == 'Debug'">true</EmitCompilerGeneratedFiles>
     <NoWarn>$(NoWarn);XC0022</NoWarn>
+    <!-- This sample uses deprecated APIs - use Runtime inflation -->
+    <MauiXamlInflator>Runtime</MauiXamlInflator>
     <!-- Disable multi-RID builds to workaround a parallel build issue -->
     <RuntimeIdentifier Condition="$(TargetFramework.Contains('-maccatalyst'))">maccatalyst-x64</RuntimeIdentifier>
     <RuntimeIdentifier Condition="$(TargetFramework.Contains('-maccatalyst')) and '$([System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture)' == 'arm64'">maccatalyst-arm64</RuntimeIdentifier>

src/Controls/samples/Controls.Sample.Profiling/Startup.cs

@@ -1,10 +1,7 @@
 using Microsoft.Maui;
 using Microsoft.Maui.Controls.Hosting;
-using Microsoft.Maui.Controls.Xaml;
 using Microsoft.Maui.Hosting;
 
-[assembly: XamlCompilation(XamlCompilationOptions.Compile)]
-
 namespace Maui.Controls.Sample.Profiling
 {
 	public static class MauiProgram

src/Controls/samples/Controls.Sample/Maui.Controls.Sample.csproj

@@ -92,4 +92,53 @@
 
   <Import Project="$(MauiSrcDirectory)Maui.InTree.props" Condition=" '$(UseMaui)' != 'true' " />
 
+  <!-- These XAML files have XSG parsing issues, use Runtime inflator until fixed -->
+  <!-- Must be after Maui.InTree.props to properly override the globbed items -->
+  <ItemGroup>
+    <MauiXaml Remove="Pages/Controls/SwipeViewGalleries/*.xaml;Pages/Others/StyleSheetsPage.xaml;Pages/Others/TwoPaneViewPage.xaml;Pages/Controls/ButtonPage.xaml;Pages/Controls/RadioButtonGalleries/RadioButtonContentGallery.xaml" />
+    <MauiXaml Include="Pages/Controls/SwipeViewGalleries/*.xaml" Inflator="Runtime" />
+    <MauiXaml Include="Pages/Others/StyleSheetsPage.xaml" Inflator="Runtime" />
+    <MauiXaml Include="Pages/Others/TwoPaneViewPage.xaml" Inflator="Runtime" />
+    <MauiXaml Include="Pages/Controls/ButtonPage.xaml" Inflator="Runtime" />
+    <MauiXaml Include="Pages/Controls/RadioButtonGalleries/RadioButtonContentGallery.xaml" Inflator="Runtime" />
+  </ItemGroup>
+
+  <!-- These XAML files use obsolete APIs (Device, NamedSize) intentionally for demonstration -->
+  <ItemGroup>
+    <MauiXaml Update="AppResources.xaml" NoWarn="0612" />
+    <MauiXaml Update="Controls/CardView/CardView.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/AppShell.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Compatibility/ListViewPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/CompatibilityPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Controls/CollectionViewGalleries/CarouselViewGalleries/CarouselViewPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Controls/CollectionViewGalleries/SelectionGalleries/VisualStatesGallery.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Controls/EditorPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Controls/IndicatorPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Controls/RadioButtonGalleries/ContentProperties.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Controls/RadioButtonGalleries/RadioButtonGroupGalleryPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Controls/ShapesGalleries/ClipCornerRadiusGallery.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Controls/ShapesGalleries/ClipGallery.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Controls/ShapesGalleries/InvalidateClipGallery.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Controls/SliderPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Controls/StepperPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/ControlsPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Core/BorderGalleries/BorderLayout.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Core/DispatcherPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Core/GesturesPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Core/ShadowGalleries/ShadowPlaygroundPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/CorePage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Layouts/FlexLayoutPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Layouts/ScrollViewPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/Layouts/ScrollViewPages/ScrollToEndPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/LayoutsPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/MainPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/OthersPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/PlatformSpecifics/Windows/WindowsDragAndDropCustomization.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/PlatformSpecifics/iOS/iOSDragAndDropRequestFullSize.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/PlatformSpecificsPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/UserInterface/FontsPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/UserInterface/VisualStatesPage.xaml" NoWarn="0612" />
+    <MauiXaml Update="Pages/UserInterfacePage.xaml" NoWarn="0612" />
+  </ItemGroup>
+
 </Project>

src/Controls/samples/Controls.Sample/Pages/AppShell.xaml.cs

@@ -18,7 +18,7 @@ public AppShell()
 
 		public string ShellTitle { get; set; } = "Welcome to Shell";
 
-		void OnChangeTabBarBackgroundColor(object sender, EventArgs e)
+		void OnChangeTabBarBackgroundColor(object? sender, EventArgs e)
 		{
 			var random = new Random();
 

src/Controls/samples/Controls.Sample/Pages/Compatibility/ListViewGalleries/ListViewContextActions.xaml.cs

@@ -17,15 +17,15 @@ public ListViewContextActions()
 					.ToList();
 		}
 
-		private void OnDetailClicked(object sender, EventArgs e)
+		private void OnDetailClicked(object? sender, EventArgs e)
 		{
-			var mi = ((MenuItem)sender);
+			var mi = ((MenuItem)sender!);
 			DisplayAlertAsync("Detail Action", $"Details for item {mi.CommandParameter}", "OK");
 		}
 
-		private void OnDeleteClicked(object sender, EventArgs e)
+		private void OnDeleteClicked(object? sender, EventArgs e)
 		{
-			var mi = ((MenuItem)sender);
+			var mi = ((MenuItem)sender!);
 			DisplayAlertAsync("Delete Action", $"Deleting item {mi.CommandParameter}!", "OK");
 		}
 

src/Controls/samples/Controls.Sample/Pages/Compatibility/TabbedPageGalleryMainPage.xaml.cs

@@ -22,7 +22,7 @@ void SetNewMainPage(Page page)
 			Application.Current!.Windows[0].Page = page;
 		}
 
-		void OnTabbedPageAsRoot(object sender, EventArgs e)
+		void OnTabbedPageAsRoot(object? sender, EventArgs e)
 		{
 			var topTabs =
 				new TabbedPage()
@@ -37,7 +37,7 @@ void OnTabbedPageAsRoot(object sender, EventArgs e)
 			SetNewMainPage(topTabs);
 		}
 
-		void OnSetToBottomTabs(object sender, EventArgs e)
+		void OnSetToBottomTabs(object? sender, EventArgs e)
 		{
 			var bottomTabs = new TabbedPage()
 			{
@@ -53,60 +53,60 @@ void OnSetToBottomTabs(object sender, EventArgs e)
 			this.Window!.Page = bottomTabs;
 		}
 
-		void OnChangeTabIndex(object sender, EventArgs e)
+		void OnChangeTabIndex(object? sender, EventArgs e)
 		{
 			GetTabbedPage().CurrentPage = GetTabbedPage().Children[1];
 		}
 
-		void OnToggleTabBar(object sender, EventArgs e)
+		void OnToggleTabBar(object? sender, EventArgs e)
 		{
 			if ((GetTabbedPage().BarBackground as SolidColorBrush)?.Color == SolidColorBrush.Purple.Color)
 				GetTabbedPage().BarBackground = null;
 			else
 				GetTabbedPage().BarBackground = SolidColorBrush.Purple;
 		}
 
-		void OnToggleTabBarTextColor(object sender, EventArgs e)
+		void OnToggleTabBarTextColor(object? sender, EventArgs e)
 		{
 			if (GetTabbedPage().BarTextColor == Colors.Green)
 				GetTabbedPage().BarTextColor = null;
 			else
 				GetTabbedPage().BarTextColor = Colors.Green;
 		}
 
-		void OnToggleTabItemUnSelectedColor(object sender, EventArgs e)
+		void OnToggleTabItemUnSelectedColor(object? sender, EventArgs e)
 		{
 			if (GetTabbedPage().UnselectedTabColor == Colors.Blue)
 				GetTabbedPage().UnselectedTabColor = null;
 			else
 				GetTabbedPage().UnselectedTabColor = Colors.Blue;
 		}
 
-		void OnToggleTabItemSelectedColor(object sender, EventArgs e)
+		void OnToggleTabItemSelectedColor(object? sender, EventArgs e)
 		{
 			if (GetTabbedPage().SelectedTabColor == Colors.Pink)
 				GetTabbedPage().SelectedTabColor = null;
 			else
 				GetTabbedPage().SelectedTabColor = Colors.Pink;
 		}
 
-		void OnRemoveTab(object sender, EventArgs e)
+		void OnRemoveTab(object? sender, EventArgs e)
 		{
 			if (GetTabbedPage().Children.LastOrDefault() is TabbedPageGalleryMainPage mainPage)
 			{
 				GetTabbedPage().Children.Remove(mainPage);
 			}
 		}
 
-		void OnRemoveAllTabs(object sender, EventArgs e)
+		void OnRemoveAllTabs(object? sender, EventArgs e)
 		{
 			while (GetTabbedPage().Children.LastOrDefault() is TabbedPageGalleryMainPage mainPage)
 			{
 				GetTabbedPage().Children.Remove(mainPage);
 			}
 		}
 
-		void OnAddTab(object sender, EventArgs e)
+		void OnAddTab(object? sender, EventArgs e)
 		{
 			GetTabbedPage()
 				.Children

src/Controls/samples/Controls.Sample/Pages/Controls/ButtonPage.xaml.cs

@@ -19,12 +19,12 @@ public ButtonPage()
 			BindingContext = new ButtonPageViewModel();
 		}
 
-		void OnButtonClicked(object sender, System.EventArgs e)
+		void OnButtonClicked(object? sender, System.EventArgs e)
 		{
 			Debug.WriteLine("Clicked");
 		}
 
-		void Button_Clicked(System.Object sender, System.EventArgs e)
+		void Button_Clicked(System.Object? sender, System.EventArgs e)
 		{
 			if (ImageSourceButton.ImageSource is null)
 			{
@@ -36,7 +36,7 @@ void Button_Clicked(System.Object sender, System.EventArgs e)
 			}
 		}
 
-		void OnPositionChange(object sender, System.EventArgs e)
+		void OnPositionChange(object? sender, System.EventArgs e)
 		{
 			var newPosition = ((int)positionChange.ContentLayout.Position) + 1;
 
@@ -48,21 +48,21 @@ void OnPositionChange(object sender, System.EventArgs e)
 					positionChange.ContentLayout.Spacing);
 		}
 
-		void OnDecreaseSpacing(object sender, System.EventArgs e)
+		void OnDecreaseSpacing(object? sender, System.EventArgs e)
 		{
 			positionChange.ContentLayout =
 				new Button.ButtonContentLayout(positionChange.ContentLayout.Position,
 					positionChange.ContentLayout.Spacing - 1);
 		}
 
-		void OnIncreasingSpacing(object sender, System.EventArgs e)
+		void OnIncreasingSpacing(object? sender, System.EventArgs e)
 		{
 			positionChange.ContentLayout =
 				new Button.ButtonContentLayout(positionChange.ContentLayout.Position,
 					positionChange.ContentLayout.Spacing + 1);
 		}
 
-		void OnLineBreakModeButtonClicked(object sender, System.EventArgs e)
+		void OnLineBreakModeButtonClicked(object? sender, System.EventArgs e)
 		{
 			LineBreakModeButton.LineBreakMode = ImageLineBreakModeButton.LineBreakMode = SelectLineBreakMode();
 		}
@@ -90,13 +90,13 @@ LineBreakMode SelectLineBreakMode()
 
 		int _backgroundCount;
 
-		void OnBackgroundButtonClicked(object sender, System.EventArgs e)
+		void OnBackgroundButtonClicked(object? sender, System.EventArgs e)
 		{
 			BackgroundButton.Text = $"Background tapped {_backgroundCount} times";
 			_backgroundCount++;
 		}
 
-		void OnChangeBrushButtonClicked(System.Object sender, System.EventArgs e)
+		void OnChangeBrushButtonClicked(System.Object? sender, System.EventArgs e)
 		{
 			UpdateButtonBrush();
 		}

src/Controls/samples/Controls.Sample/Pages/Controls/CheckBoxPage.xaml.cs

@@ -13,7 +13,7 @@ public CheckBoxPage()
 			UpdateControls();
 		}
 
-		void OnChangeIsCheckedButtonClicked(object sender, EventArgs e)
+		void OnChangeIsCheckedButtonClicked(object? sender, EventArgs e)
 		{
 			_isGreen = !_isGreen;
 			UpdateControls();

src/Controls/samples/Controls.Sample/Pages/Controls/CollectionViewGalleries/CarouselViewGalleries/CarouselViewPage.xaml.cs

@@ -9,7 +9,7 @@ public CarouselViewPage()
 			InitializeComponent();
 		}
 
-		async void TapGestureRecognizer_Tapped(object sender, EventArgs e)
+		async void TapGestureRecognizer_Tapped(object? sender, EventArgs e)
 		{
 			await DisplayAlertAsync("Item", "Tapped", "Successfully");
 		}

src/Controls/samples/Controls.Sample/Pages/Controls/CollectionViewGalleries/DataTemplateSelectorGalleries/VariedSizeDataTemplateSelectorGallery.xaml.cs

@@ -64,15 +64,15 @@ public bool ShouldTriggerReset
 			set => SetValue(ref _shouldTriggerReset, value);
 		}
 
-		void Insert_OnClicked(object sender, EventArgs e)
+		void Insert_OnClicked(object? sender, EventArgs e)
 		{
 			if (!IsValid(out var index))
 				return;
 
 			Items.Insert(index, CreateDrink());
 		}
 
-		void Add_OnClicked(object sender, EventArgs e)
+		void Add_OnClicked(object? sender, EventArgs e)
 		{
 			if (!IsValid(out var _))
 				return;
@@ -89,7 +89,7 @@ void SetValue<T>(ref T backingField, in T value, [CallerMemberName] string calle
 			OnPropertyChanged(callerName);
 		}
 
-		void Remove_OnClicked(object sender, EventArgs e)
+		void Remove_OnClicked(object? sender, EventArgs e)
 		{
 			if (!IsValid(out var index))
 				return;

src/Controls/samples/Controls.Sample/Pages/Controls/CollectionViewGalleries/EmptyViewGalleries/EmptyViewRTLGallery.xaml.cs

@@ -22,7 +22,7 @@ public EmptyViewRTLGallery()
 			SearchBar.SearchCommand = new Command(() => _demoFilteredItemSource.FilterItems(SearchBar.Text));
 		}
 
-		void OnPickerSelectedIndexChanged(object sender, EventArgs e)
+		void OnPickerSelectedIndexChanged(object? sender, EventArgs e)
 		{
 			switch (Picker.SelectedIndex)
 			{

src/Controls/samples/Controls.Sample/Pages/Controls/CollectionViewGalleries/ExampleTemplates.cs

@@ -539,7 +539,7 @@ public static DataTemplate GroupFooterTemplate()
 			});
 		}
 
-		static void More_Clicked(object sender, EventArgs e)
+		static void More_Clicked(object? sender, EventArgs e)
 		{
 			throw new NotImplementedException();
 		}