Include Startup class (#436)

* Implement IStartup

* Clean up code

* Move the static Current into MauiApp

* Add missing SearchBar handler mapping

* Don't need this anymore

* Pass the handler along on iOS

* Lots more perf fixes

* Remove App.SetHandlerContext

* Fix tests

* Fix catalyst

* revert

* Fixed build errors

* Fix the updated SearchBar

* Fix net6 single project

* Add IHostBuilderStartup

Co-authored-by: Matthew Leibowitz <mattleibow@live.com>

src/Compatibility/Core/src/Android/AppCompat/Platform.cs

@@ -313,6 +313,7 @@ namespace Microsoft.Maui.Controls.Compatibility.Platform.Android.AppCompat
 				try
 				{
 					handler = Forms.MauiContext.Handlers.GetHandler(element.GetType());
+					handler.SetMauiContext(Forms.MauiContext);
 				}
 				catch
 				{
@@ -340,10 +341,7 @@ namespace Microsoft.Maui.Controls.Compatibility.Platform.Android.AppCompat
 				else if (handler is IVisualElementRenderer ver)
 					renderer = ver;
 				else if (handler is IAndroidViewHandler vh)
-				{
-					vh.SetContext(context);
 					renderer = new HandlerToRendererShim(vh);
-				}
 			}
 
 			renderer.SetElement(element);

src/Compatibility/Core/src/AppHostBuilderExtensions.cs

@@ -12,15 +12,15 @@ namespace Microsoft.Maui.Controls.Compatibility
 			var defaultHandlers = new List<Type>
 			{
 				typeof(Button),
+				typeof(ContentPage),
 				typeof(Editor),
 				typeof(Entry),
-				typeof(ContentPage),
-				typeof(Page),
 				typeof(Label),
+				typeof(Page),
+				typeof(SearchBar),
 				typeof(Slider),
 				typeof(Stepper),
 				typeof(Switch),
-				typeof(SearchBar)
 			};
 
 			Forms.RegisterCompatRenderers(

src/Compatibility/Core/src/iOS/Platform.cs

@@ -239,6 +239,7 @@ namespace Microsoft.Maui.Controls.Compatibility.Platform.iOS
 				try
 				{
 					handler = Forms.ActivationState.Context.Handlers.GetHandler(element.GetType());
+					handler.SetMauiContext(Forms.ActivationState.Context);
 				}
 				catch
 				{

src/Controls/samples/Controls.Sample.Droid/MainApplication.cs

@@ -6,7 +6,7 @@ using Microsoft.Maui;
 namespace Maui.Controls.Sample.Droid
 {
 	[Application]
-	public class MainApplication : MauiApplication<MyApp>
+	public class MainApplication : MauiApplication<Startup>
 	{
 		public MainApplication(IntPtr handle, JniHandleOwnership ownerShip) : base(handle, ownerShip)
 		{

src/Controls/samples/Controls.Sample.MacCatalyst/AppDelegate.cs

@@ -11,7 +11,7 @@ using Maui.Controls.Sample;
 namespace Sample.MacCatalyst
 {
 	[Register("AppDelegate")]
-	public class AppDelegate : MauiUIApplicationDelegate<MyApp>
+	public class AppDelegate : MauiUIApplicationDelegate<Startup>
 	{
 	}
 }

src/Controls/samples/Controls.Sample.SingleProject/Android/MainActivity.cs

@@ -6,6 +6,5 @@ namespace Maui.Controls.Sample.SingleProject
 	[Activity(Theme = "@style/AppTheme.NoActionBar", MainLauncher = true)]
 	public class MainActivity : MauiAppCompatActivity
 	{
-
 	}
 }

src/Controls/samples/Controls.Sample.SingleProject/Android/MainApplication.cs

@@ -6,9 +6,9 @@ using Microsoft.Maui;
 namespace Maui.Controls.Sample.SingleProject
 {
 	[Application]
-	public class MainApplication : MauiApplication<MyApp>
+	public class MainApplication : MauiApplication<Startup>
 	{
-		public MainApplication(IntPtr handle, JniHandleOwnership ownerShip) : base(handle, ownerShip)
+		public MainApplication(IntPtr handle, JniHandleOwnership ownership) : base(handle, ownership)
 		{
 		}
 	}

src/Controls/samples/Controls.Sample.SingleProject/MacCatalyst/AppDelegate.cs

@@ -4,8 +4,7 @@ using Microsoft.Maui;
 namespace Maui.Controls.Sample.SingleProject
 {
 	[Register("AppDelegate")]
-	public class AppDelegate : MauiUIApplicationDelegate<MyApp>
+	public class AppDelegate : MauiUIApplicationDelegate<Startup>
 	{
-
 	}
 }

src/Controls/samples/Controls.Sample.SingleProject/MainPage.cs

@@ -16,4 +16,4 @@ namespace Maui.Controls.Sample.SingleProject
 
 		public IView View { get => (IView)Content; set => Content = (View)value; }
 	}
-}
+}

src/Controls/samples/Controls.Sample.SingleProject/MainWindow.cs

@@ -1,16 +1,16 @@
-using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Maui;
+using Microsoft.Maui;
 
 namespace Maui.Controls.Sample.SingleProject
 {
 	public class MainWindow : IWindow
 	{
-		public IPage Page { get; set; }
-		public IMauiContext MauiContext { get; set; }
-
 		public MainWindow()
 		{
-			Page = App.Current.Services.GetService<MainPage>();
+			Page = new MainPage();
 		}
+
+		public IPage Page { get; set; }
+
+		public IMauiContext MauiContext { get; set; }
 	}
-}
+}

src/Controls/samples/Controls.Sample.SingleProject/MyApp.cs

@@ -1,26 +1,17 @@
-using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Maui;
-using Microsoft.Maui.Hosting;
+using Microsoft.Maui;
 
 namespace Maui.Controls.Sample.SingleProject
 {
 	public class MyApp : MauiApp
 	{
-		public override IAppHostBuilder CreateBuilder() => 
-			base.CreateBuilder().ConfigureServices((ctx, services) =>
-				{
-					services.AddTransient<MainPage>();
-					services.AddTransient<IWindow, MainWindow>();
-				});
-
 		public override IWindow CreateWindow(IActivationState state)
 		{
-#if (ANDROID || IOS)
-
+#if ANDROID || IOS
 			// This will probably go into a compatibility app or window
 			Microsoft.Maui.Controls.Compatibility.Forms.Init(state);
 #endif
-			return Services.GetService<IWindow>();
+
+			return new MainWindow();
 		}
 	}
 }

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

@@ -0,0 +1,16 @@
+using Microsoft.Maui;
+using Microsoft.Maui.Controls.Compatibility;
+using Microsoft.Maui.Hosting;
+
+namespace Maui.Controls.Sample.SingleProject
+{
+	public class Startup : IStartup
+	{
+		public void Configure(IAppHostBuilder appBuilder)
+		{
+			appBuilder
+				.RegisterCompatibilityRenderers()
+				.UseMauiApp<MyApp>();
+		}
+	}
+}

src/Controls/samples/Controls.Sample.SingleProject/iOS/AppDelegate.cs

@@ -4,8 +4,7 @@ using Microsoft.Maui;
 namespace Maui.Controls.Sample.SingleProject
 {
 	[Register("AppDelegate")]
-	public class AppDelegate : MauiUIApplicationDelegate<MyApp>
+	public class AppDelegate : MauiUIApplicationDelegate<Startup>
 	{
-
 	}
 }

src/Controls/samples/Controls.Sample.iOS/AppDelegate.cs

@@ -11,7 +11,7 @@ using Maui.Controls.Sample;
 namespace Sample.iOS
 {
 	[Register("AppDelegate")]
-	public class AppDelegate : MauiUIApplicationDelegate<MyApp>
+	public class AppDelegate : MauiUIApplicationDelegate<Startup>
 	{
 	}
 }

src/Controls/samples/Controls.Sample/MainWindow.cs

@@ -1,20 +1,13 @@
 using Maui.Controls.Sample.Controls;
-using Maui.Controls.Sample.Pages;
-using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Maui;
-using Microsoft.Maui.Controls;
 
 namespace Maui.Controls.Sample
 {
 	public class MainWindow : Window
 	{
-		public MainWindow() : this(App.Current.Services.GetRequiredService<IPage>())
-		{
-		}
-
 		public MainWindow(IPage page)
 		{
 			Page = page;
 		}
 	}
-}
+}

src/Controls/samples/Controls.Sample/MyApp.cs

@@ -1,65 +1,22 @@
 using System;
-using System.Collections.Generic;
-using Maui.Controls.Sample.Pages;
 using Maui.Controls.Sample.Services;
-using Maui.Controls.Sample.ViewModel;
-using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Maui;
-using Microsoft.Maui.Controls;
 using Microsoft.Maui.Controls.Compatibility;
-using Microsoft.Maui.Hosting;
 
 namespace Maui.Controls.Sample
 {
 	public class MyApp : MauiApp
 	{
-		public readonly static bool UseXamlPage = false;
+		public MyApp(ITextService textService)
+		{
+			Console.WriteLine($"The injected text service had a message: '{textService.GetText()}'");
+		}
 
-		public override IAppHostBuilder CreateBuilder() =>
-			base.CreateBuilder()
-				.RegisterCompatibilityRenderers()
-				.ConfigureAppConfiguration((hostingContext, config) =>
-				{
-					config.AddInMemoryCollection(new Dictionary<string, string>
-					{
-						{ "MyKey", "Dictionary MyKey Value" },
-						{ ":Title", "Dictionary_Title" },
-						{ "Position:Name", "Dictionary_Name" },
-						{ "Logging:LogLevel:Default", "Warning" }
-					});
-				})
-				.ConfigureServices((hostingContext, services) =>
-				{
-					services.AddSingleton<ITextService, TextService>();
-					services.AddTransient<MainPageViewModel>();
-					if (UseXamlPage)
-						services.AddTransient<IPage, XamlPage>();
-					else
-						services.AddTransient<IPage, MainPage>();
-					services.AddTransient<IWindow, MainWindow>();
-				})
-				.ConfigureFonts((hostingContext, fonts) =>
-				{
-					fonts.AddFont("dokdo_regular.ttf", "Dokdo");
-				});
-
-		//IAppState state
 		public override IWindow CreateWindow(IActivationState state)
 		{
 			Forms.Init(state);
 			return Services.GetRequiredService<IWindow>();
 		}
 	}
-
-	//to use DI ServiceCollection and not the MAUI one
-	public class DIExtensionsServiceProviderFactory : IServiceProviderFactory<ServiceCollection>
-	{
-		public ServiceCollection CreateBuilder(IServiceCollection services)
-			=> new ServiceCollection { services };
-
-		public IServiceProvider CreateServiceProvider(ServiceCollection containerBuilder)
-			=> containerBuilder.BuildServiceProvider();
-	}
 }

src/Controls/samples/Controls.Sample/Pages/MainPage.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using Maui.Controls.Sample.ViewModel;
-using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Maui;
 using Microsoft.Maui.Controls;
 
@@ -11,14 +10,10 @@ namespace Maui.Controls.Sample.Pages
 	{
 		MainPageViewModel _viewModel;
 
-		public MainPage() : this(App.Current.Services.GetService<MainPageViewModel>())
-		{
-
-		}
-
 		public MainPage(MainPageViewModel viewModel)
 		{
 			BindingContext = _viewModel = viewModel;
+
 			SetupMauiLayout();
 			//SetupCompatibilityLayout();
 		}
@@ -98,8 +93,7 @@ namespace Maui.Controls.Sample.Pages
 			};
 
 			verticalStack.Add(entry);
-
-			verticalStack.Add(new Entry { Text = "Entry", TextColor = Color.DarkRed });
+			verticalStack.Add(new Entry { Text = "Entry", TextColor = Color.DarkRed, FontFamily = "Dokdo" });
 			verticalStack.Add(new Entry { IsPassword = true, TextColor = Color.Black });
 			verticalStack.Add(new Entry { IsTextPredictionEnabled = false });
 			verticalStack.Add(new Entry { Placeholder = "This should be placeholder text" });
@@ -152,7 +146,10 @@ namespace Maui.Controls.Sample.Pages
 
 			verticalStack.Add(new Image() { Source = "dotnet_bot.png" });
 
-			Content = verticalStack;
+			Content = new ScrollView
+			{
+				Content = verticalStack
+			};
 		}
 
 		void SetupCompatibilityLayout()

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

@@ -0,0 +1,64 @@
+using System;
+using System.Collections.Generic;
+using Maui.Controls.Sample.Pages;
+using Maui.Controls.Sample.Services;
+using Maui.Controls.Sample.ViewModel;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyInjection.Extensions;
+using Microsoft.Maui;
+using Microsoft.Maui.Controls.Compatibility;
+using Microsoft.Maui.Hosting;
+
+namespace Maui.Controls.Sample
+{
+	public class Startup : IStartup
+	{
+		public readonly static bool UseXamlPage = false;
+
+		public void Configure(IAppHostBuilder appBuilder)
+		{
+			appBuilder
+				.RegisterCompatibilityRenderers()
+				.UseMauiApp<MyApp>()
+				.ConfigureAppConfiguration((hostingContext, config) =>
+				{
+					config.AddInMemoryCollection(new Dictionary<string, string>
+					{
+						{"MyKey", "Dictionary MyKey Value"},
+						{":Title", "Dictionary_Title"},
+						{"Position:Name", "Dictionary_Name" },
+						{"Logging:LogLevel:Default", "Warning"}
+					});
+				})
+				.UseMauiServiceProviderFactory(true)
+				//.UseServiceProviderFactory(new DIExtensionsServiceProviderFactory())
+				.ConfigureServices((hostingContext, services) =>
+				{
+					services.AddSingleton<ITextService, TextService>();
+					services.AddTransient<MainPageViewModel>();
+
+					if (UseXamlPage)
+						services.AddTransient<IPage, XamlPage>();
+					else
+						services.AddTransient<IPage, MainPage>();
+
+					services.AddTransient<IWindow, MainWindow>();
+				})
+				.ConfigureFonts((hostingContext, fonts) =>
+				{
+					fonts.AddFont("dokdo_regular.ttf", "Dokdo");
+				});
+		}
+
+		// To use DI ServiceCollection and not the MAUI one
+		public class DIExtensionsServiceProviderFactory : IServiceProviderFactory<ServiceCollection>
+		{
+			public ServiceCollection CreateBuilder(IServiceCollection services)
+				=> new ServiceCollection { services };
+
+			public IServiceProvider CreateServiceProvider(ServiceCollection containerBuilder)
+				=> containerBuilder.BuildServiceProvider();
+		}
+	}
+}

src/Controls/samples/Controls.Sample/ViewModel/MainPageViewModel.cs

@@ -1,44 +1,29 @@
-using System.Collections.Generic;
-using System.Linq;
+using System;
 using Maui.Controls.Sample.Services;
 using Microsoft.Extensions.Configuration;
-using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.Logging;
-using Microsoft.Maui;
 
 namespace Maui.Controls.Sample.ViewModel
 {
 	public class MainPageViewModel : ViewModelBase
 	{
-		private readonly IConfiguration Configuration;
-		ITextService textService;
-
-		public MainPageViewModel() : this(new ITextService[] { App.Current.Services.GetService<ITextService>() })
-		{
-		}
-
-		public MainPageViewModel(IEnumerable<ITextService> textServices)
-		{
-			Configuration = App.Current.Services.GetService<IConfiguration>();
-
-			//var logger = App.Current.Services.GetService<ILogger<MainPageViewModel>>();
-
-			//logger.LogInformation("hello");
-
-			textService = textServices.FirstOrDefault();
-			Text = textService.GetText();
-		}
-
-		//public MainPageViewModel(ITextService textService)
-		//{
-		//	Text = textService.GetText();
-		//}
-
+		readonly IConfiguration _configuration;
+		readonly ITextService _textService;
 		string _text;
+
+		public MainPageViewModel(IConfiguration configuration, ITextService textService)
+		{
+			_configuration = configuration;
+			_textService = textService;
+
+			Console.WriteLine($"Value from config: {_configuration["MyKey"]}");
+
+			Text = _textService.GetText();
+		}
+
 		public string Text
 		{
 			get => _text;
 			set => SetProperty(ref _text, value);
 		}
 	}
-}
+}

src/Controls/src/Core/HandlerImpl/SearchBar.Impl.cs

@@ -4,17 +4,6 @@
 	{
 		Font? _font;
 
-		Font IText.Font
-		{
-			get
-			{
-				if (_font == null)
-				{
-					_font = Font.OfSize(FontFamily, FontSize).WithAttributes(FontAttributes);
-				}
-
-				return _font.Value;
-			}
-		}
+		Font IText.Font => _font ??= Font.OfSize(FontFamily, FontSize).WithAttributes(FontAttributes);
 	}
 }

src/Core/src/App.cs

@@ -1,50 +1,14 @@
 using System;
-using System.Collections.Generic;
-using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Maui.Hosting;
 
 namespace Microsoft.Maui
 {
 	public abstract class App : IApp
 	{
-		IServiceProvider? _serviceProvider;
-		IMauiContext? _context;
-
-		protected App()
-		{
-			if (Current != null)
-				throw new InvalidOperationException($"Only one {nameof(App)} instance is allowed");
-			Current = this;
-		}
-
-		public static App? Current { get; internal set; }
-
-		public IServiceProvider? Services => _serviceProvider;
-
-		public IMauiContext? Context => _context;
-
-		//move to abstract
-		public virtual IAppHostBuilder CreateBuilder() => CreateDefaultBuilder();
+		public IServiceProvider? Services { get; private set; }
 
 		internal void SetServiceProvider(IServiceProvider provider)
 		{
-			_serviceProvider = provider;
-			SetHandlerContext(provider.GetService<IMauiContext>());
-		}
-
-		internal void SetHandlerContext(IMauiContext? context)
-		{
-			_context = context;
-		}
-
-		public static IAppHostBuilder CreateDefaultBuilder()
-		{
-			var builder = new AppHostBuilder();
-
-			builder.UseMauiHandlers();
-			builder.UseFonts();
-
-			return builder;
+			Services = provider;
 		}
 	}
-}
+}

src/Core/src/Core/IStartup.cs

@@ -0,0 +1,29 @@
+using Microsoft.Maui.Hosting;
+
+namespace Microsoft.Maui
+{
+	/// <summary>
+	/// Startup allow to configure and instantiate application services.
+	/// </summary>
+	public interface IStartup
+	{
+		/// <summary>
+		/// Configures the application.
+		/// Configure are called by the .NET MAUI Core runtime when the app starts.
+		/// </summary>
+		/// <param name="appBuilder">Defines a class that provides the mechanisms to configure an application's dependencies.</param>
+		void Configure(IAppHostBuilder appBuilder);
+	}
+
+	/// <summary>
+	/// Allow to create a custom IAppHostBuilder instance.
+	/// </summary>
+	public interface IHostBuilderStartup
+	{
+		/// <summary>
+		/// Create and configure a builder object.
+		/// </summary>
+		/// <returns>The new instance of the IAppHostBuilder.</returns>
+		public IAppHostBuilder CreateHostBuilder();
+	}
+}

src/Core/src/Handlers/Button/ButtonHandler.Android.cs

@@ -55,9 +55,9 @@ namespace Microsoft.Maui.Handlers
 
 		public static void MapFont(ButtonHandler handler, IButton button)
 		{
-			var services = App.Current?.Services
-				?? throw new InvalidOperationException($"Unable to find service provider, the App.Current.Services was null.");
-			var fontManager = services.GetRequiredService<IFontManager>();
+			_ = handler.Services ?? throw new InvalidOperationException($"{nameof(Services)} should have been set by base class.");
+
+			var fontManager = handler.Services.GetRequiredService<IFontManager>();
 
 			handler.TypedNativeView?.UpdateFont(button, fontManager);
 		}

src/Core/src/Handlers/Button/ButtonHandler.cs

@@ -15,7 +15,7 @@ namespace Microsoft.Maui.Handlers
 
 		}
 
-		public ButtonHandler(PropertyMapper mapper) : base(mapper ?? ButtonMapper)
+		public ButtonHandler(PropertyMapper? mapper = null) : base(mapper ?? ButtonMapper)
 		{
 		}
 	}

src/Core/src/Handlers/Button/ButtonHandler.iOS.cs

@@ -61,9 +61,9 @@ namespace Microsoft.Maui.Handlers
 
 		public static void MapFont(ButtonHandler handler, IButton button)
 		{
-			var services = App.Current?.Services ??
-				throw new InvalidOperationException($"Unable to find service provider, the App.Current.Services was null.");
-			var fontManager = services.GetRequiredService<IFontManager>();
+			_ = handler.Services ?? throw new InvalidOperationException($"{nameof(Services)} should have been set by base class.");
+
+			var fontManager = handler.Services.GetRequiredService<IFontManager>();
 
 			handler.TypedNativeView?.UpdateFont(button, fontManager);
 		}

src/Core/src/Handlers/Editor/EditorHandler.cs

@@ -14,7 +14,7 @@
 
 		}
 
-		public EditorHandler(PropertyMapper mapper) : base(mapper ?? EditorMapper)
+		public EditorHandler(PropertyMapper? mapper = null) : base(mapper ?? EditorMapper)
 		{
 
 		}

src/Core/src/Handlers/Entry/EntryHandler.Android.cs

@@ -67,9 +67,9 @@ namespace Microsoft.Maui.Handlers
 
 		public static void MapFont(EntryHandler handler, IEntry entry)
 		{
-			var services = App.Current?.Services
-				?? throw new InvalidOperationException($"Unable to find service provider, the App.Current.Services was null.");
-			var fontManager = services.GetRequiredService<IFontManager>();
+			_ = handler.Services ?? throw new InvalidOperationException($"{nameof(Services)} should have been set by base class.");
+
+			var fontManager = handler.Services.GetRequiredService<IFontManager>();
 
 			handler.TypedNativeView?.UpdateFont(entry, fontManager);
 		}

src/Core/src/Handlers/Entry/EntryHandler.cs

@@ -20,7 +20,7 @@
 
 		}
 
-		public EntryHandler(PropertyMapper mapper) : base(mapper ?? EntryMapper)
+		public EntryHandler(PropertyMapper? mapper = null) : base(mapper ?? EntryMapper)
 		{
 
 		}

src/Core/src/Handlers/Entry/EntryHandler.iOS.cs

@@ -103,9 +103,9 @@ namespace Microsoft.Maui.Handlers
 
 		public static void MapFont(EntryHandler handler, IEntry entry)
 		{
-			var services = App.Current?.Services
-				?? throw new InvalidOperationException($"Unable to find service provider, the App.Current.Services was null.");
-			var fontManager = services.GetRequiredService<IFontManager>();
+			_ = handler.Services ?? throw new InvalidOperationException($"{nameof(Services)} should have been set by base class.");
+
+			var fontManager = handler.Services.GetRequiredService<IFontManager>();
 
 			handler.TypedNativeView?.UpdateFont(entry, fontManager);
 		}

src/Core/src/Handlers/IViewHandler.Android.cs

@@ -5,8 +5,6 @@ namespace Microsoft.Maui
 {
 	public interface IAndroidViewHandler : IViewHandler
 	{
-		void SetContext(Context context);
-
 		AView? View { get; }
 	}
 }

src/Core/src/Handlers/IViewHandler.cs

@@ -1,9 +1,11 @@
+using System;
 using Microsoft.Maui;
 
 namespace Microsoft.Maui
 {
 	public interface IViewHandler
 	{
+		void SetMauiContext(IMauiContext mauiContext);
 		void SetVirtualView(IView view);
 		void UpdateValue(string property);
 		void DisconnectHandler();

src/Core/src/Handlers/Label/LabelHandler.Android.cs

@@ -68,9 +68,9 @@ namespace Microsoft.Maui.Handlers
 
 		public static void MapFont(LabelHandler handler, ILabel label)
 		{
-			var services = App.Current?.Services
-				?? throw new InvalidOperationException($"Unable to find service provider, the App.Current.Services was null.");
-			var fontManager = services.GetRequiredService<IFontManager>();
+			_ = handler.Services ?? throw new InvalidOperationException($"{nameof(Services)} should have been set by base class.");
+
+			var fontManager = handler.Services.GetRequiredService<IFontManager>();
 
 			handler.TypedNativeView?.UpdateFont(label, fontManager);
 		}

src/Core/src/Handlers/Label/LabelHandler.cs

@@ -21,7 +21,7 @@ namespace Microsoft.Maui.Handlers
 
 		}
 
-		public LabelHandler(PropertyMapper mapper) : base(mapper ?? LabelMapper)
+		public LabelHandler(PropertyMapper? mapper = null) : base(mapper ?? LabelMapper)
 		{
 
 		}

src/Core/src/Handlers/Label/LabelHandler.iOS.cs

@@ -53,9 +53,9 @@ namespace Microsoft.Maui.Handlers
 
 		public static void MapFont(LabelHandler handler, ILabel label)
 		{
-			var services = App.Current?.Services ??
-				throw new InvalidOperationException($"Unable to find service provider, the App.Current.Services was null.");
-			var fontManager = services.GetRequiredService<IFontManager>();
+			_ = handler.Services ?? throw new InvalidOperationException($"{nameof(Services)} should have been set by base class.");
+
+			var fontManager = handler.Services.GetRequiredService<IFontManager>();
 
 			handler.TypedNativeView?.UpdateFont(label, fontManager);
 		}

src/Core/src/Handlers/Layout/LayoutHandler.Android.cs

@@ -29,14 +29,14 @@ namespace Microsoft.Maui.Handlers
 
 			_ = TypedNativeView ?? throw new InvalidOperationException($"{nameof(TypedNativeView)} should have been set by base class.");
 			_ = VirtualView ?? throw new InvalidOperationException($"{nameof(VirtualView)} should have been set by base class.");
-			_ = MauiApp.Current?.Context ?? throw new InvalidOperationException($"The MauiApp.Current.Context can't be null.");
+			_ = MauiContext ?? throw new InvalidOperationException($"{nameof(MauiContext)} should have been set by base class.");
 
 			TypedNativeView.CrossPlatformMeasure = VirtualView.Measure;
 			TypedNativeView.CrossPlatformArrange = VirtualView.Arrange;
 
 			foreach (var child in VirtualView.Children)
 			{
-				TypedNativeView.AddView(child.ToNative(MauiApp.Current.Context));
+				TypedNativeView.AddView(child.ToNative(MauiContext));
 			}
 		}
 
@@ -44,9 +44,9 @@ namespace Microsoft.Maui.Handlers
 		{
 			_ = TypedNativeView ?? throw new InvalidOperationException($"{nameof(TypedNativeView)} should have been set by base class.");
 			_ = VirtualView ?? throw new InvalidOperationException($"{nameof(VirtualView)} should have been set by base class.");
-			_ = MauiApp.Current?.Context ?? throw new InvalidOperationException($"The MauiApp.Current.Context can't be null.");
+			_ = MauiContext ?? throw new InvalidOperationException($"{nameof(MauiContext)} should have been set by base class.");
 
-			TypedNativeView.AddView(child.ToNative(MauiApp.Current.Context!), 0);
+			TypedNativeView.AddView(child.ToNative(MauiContext), 0);
 		}
 
 		public void Remove(IView child)

src/Core/src/Handlers/Layout/LayoutHandler.cs

@@ -15,7 +15,7 @@ namespace Microsoft.Maui.Handlers
 
 		}
 
-		public LayoutHandler(PropertyMapper mapper) : base(mapper ?? LayoutMapper)
+		public LayoutHandler(PropertyMapper? mapper = null) : base(mapper ?? LayoutMapper)
 		{
 
 		}

src/Core/src/Handlers/Layout/LayoutHandler.iOS.cs

@@ -32,14 +32,14 @@ namespace Microsoft.Maui.Handlers
 
 			_ = TypedNativeView ?? throw new InvalidOperationException($"{nameof(TypedNativeView)} should have been set by base class.");
 			_ = VirtualView ?? throw new InvalidOperationException($"{nameof(VirtualView)} should have been set by base class.");
-			_ = MauiApp.Current?.Context ?? throw new InvalidOperationException($"The MauiApp.Current.Context can't be null.");
+			_ = MauiContext ?? throw new InvalidOperationException($"{nameof(MauiContext)} should have been set by base class.");
 
 			TypedNativeView.CrossPlatformMeasure = VirtualView.Measure;
 			TypedNativeView.CrossPlatformArrange = VirtualView.Arrange;
 
 			foreach (var child in VirtualView.Children)
 			{
-				TypedNativeView.AddSubview(child.ToNative(MauiApp.Current.Context));
+				TypedNativeView.AddSubview(child.ToNative(MauiContext));
 			}
 		}
 
@@ -47,9 +47,9 @@ namespace Microsoft.Maui.Handlers
 		{
 			_ = TypedNativeView ?? throw new InvalidOperationException($"{nameof(TypedNativeView)} should have been set by base class.");
 			_ = VirtualView ?? throw new InvalidOperationException($"{nameof(VirtualView)} should have been set by base class.");
-			_ = MauiApp.Current?.Context ?? throw new InvalidOperationException($"The MauiApp.Current.Context can't be null.");
+			_ = MauiContext ?? throw new InvalidOperationException($"{nameof(MauiContext)} should have been set by base class.");
 
-			TypedNativeView.AddSubview(child.ToNative(MauiApp.Current.Context));
+			TypedNativeView.AddSubview(child.ToNative(MauiContext));
 			TypedNativeView.SetNeedsLayout();
 		}
 

src/Core/src/Handlers/ProgressBar/ProgressBarHandler.cs

@@ -17,7 +17,7 @@
 
 		}
 
-		public ProgressBarHandler(PropertyMapper mapper) : base(mapper ?? ProgressMapper)
+		public ProgressBarHandler(PropertyMapper? mapper = null) : base(mapper ?? ProgressMapper)
 		{
 
 		}

src/Core/src/Handlers/SearchBar/SearchBarHandler.Android.cs

@@ -32,9 +32,9 @@ namespace Microsoft.Maui.Handlers
 
 		public static void MapFont(SearchBarHandler handler, ISearchBar searchBar)
 		{
-			var services = App.Current?.Services
-				?? throw new InvalidOperationException($"Unable to find service provider, the App.Current.Services was null.");
-			var fontManager = services.GetRequiredService<IFontManager>();
+			_ = handler.Services ?? throw new InvalidOperationException($"{nameof(Services)} should have been set by base class.");
+
+			var fontManager = handler.Services.GetRequiredService<IFontManager>();
 
 			handler.TypedNativeView?.UpdateFont(searchBar, fontManager, handler._editText);
 		}

src/Core/src/Handlers/SearchBar/SearchBarHandler.cs

@@ -16,7 +16,7 @@
 
 		}
 
-		public SearchBarHandler(PropertyMapper mapper) : base(mapper ?? SearchBarMapper)
+		public SearchBarHandler(PropertyMapper? mapper = null) : base(mapper ?? SearchBarMapper)
 		{
 
 		}

src/Core/src/Handlers/SearchBar/SearchBarHandler.iOS.cs

@@ -31,9 +31,9 @@ namespace Microsoft.Maui.Handlers
 
 		public static void MapFont(SearchBarHandler handler, ISearchBar searchBar)
 		{
-			var services = App.Current?.Services ??
-				throw new InvalidOperationException($"Unable to find service provider, the App.Current.Services was null.");
-			var fontManager = services.GetRequiredService<IFontManager>();
+			_ = handler.Services ?? throw new InvalidOperationException($"{nameof(Services)} should have been set by base class.");
+
+			var fontManager = handler.Services.GetRequiredService<IFontManager>();
 
 			handler.QueryEditor?.UpdateFont(searchBar, fontManager);
 		}

src/Core/src/Handlers/Slider/SliderHandler.cs

@@ -17,7 +17,7 @@ namespace Microsoft.Maui.Handlers
 
 		}
 
-		public SliderHandler(PropertyMapper mapper) : base(mapper ?? SliderMapper)
+		public SliderHandler(PropertyMapper? mapper = null) : base(mapper ?? SliderMapper)
 		{
 
 		}

src/Core/src/Handlers/Switch/SwitchHandler.cs

@@ -14,7 +14,7 @@ namespace Microsoft.Maui.Handlers
 
 		}
 
-		public SwitchHandler(PropertyMapper mapper) : base(mapper ?? SwitchMapper)
+		public SwitchHandler(PropertyMapper? mapper = null) : base(mapper ?? SwitchMapper)
 		{
 
 		}

src/Core/src/Handlers/View/AbstractViewHandler.Android.cs

@@ -6,9 +6,7 @@ namespace Microsoft.Maui.Handlers
 {
 	public partial class AbstractViewHandler<TVirtualView, TNativeView> : IAndroidViewHandler
 	{
-		public void SetContext(Context context) => Context = context;
-
-		public Context? Context { get; private set; }
+		public Context? Context => MauiContext?.Context;
 
 		public void SetFrame(Rectangle frame)
 		{

src/Core/src/Handlers/View/AbstractViewHandler.cs

@@ -41,6 +41,12 @@ namespace Microsoft.Maui.Handlers
 
 		public object? NativeView => TypedNativeView;
 
+		public IServiceProvider? Services => MauiContext?.Services;
+
+		public IMauiContext? MauiContext { get; private set; }
+
+		public void SetMauiContext(IMauiContext mauiContext) => MauiContext = mauiContext;
+
 		public virtual void SetVirtualView(IView view)
 		{
 			_ = view ?? throw new ArgumentNullException(nameof(view));

src/Core/src/Hosting/AppHostBuilder.cs

@@ -18,7 +18,9 @@ namespace Microsoft.Maui.Hosting
 		readonly List<Action<HostBuilderContext, IFontCollection>> _configureFontsActions = new List<Action<HostBuilderContext, IFontCollection>>();
 		readonly List<IConfigureContainerAdapter> _configureContainerActions = new List<IConfigureContainerAdapter>();
 		readonly Func<IServiceCollection> _serviceColectionFactory = new Func<IServiceCollection>(() => new MauiServiceCollection());
-		IServiceFactoryAdapter _serviceProviderFactory = new ServiceFactoryAdapter<IServiceCollection>(new MauiServiceProviderFactory());
+
+		IServiceFactoryAdapter _serviceProviderFactory = new ServiceFactoryAdapter<IServiceCollection>(new MauiServiceProviderFactory(false));
+
 		bool _hostBuilt;
 		HostBuilderContext? _hostBuilderContext;
 		IHostEnvironment? _hostEnvironment;
@@ -26,7 +28,6 @@ namespace Microsoft.Maui.Hosting
 		IServiceCollection? _services;
 		IConfiguration? _hostConfiguration;
 		IConfiguration? _appConfiguration;
-		App? _app;
 
 		public AppHostBuilder()
 		{
@@ -34,13 +35,17 @@ namespace Microsoft.Maui.Hosting
 		}
 		public IDictionary<object, object> Properties => new Dictionary<object, object>();
 
-		public IHost Build(IApp app)
+		public static IAppHostBuilder CreateDefaultAppBuilder()
 		{
-			_app = app as App;
-			return Build();
+			var builder = new AppHostBuilder();
+
+			builder.UseMauiHandlers();
+			builder.UseFonts();
+
+			return builder;
 		}
 
-		public IHost Build()
+		public IAppHost Build()
 		{
 			_services = _serviceColectionFactory();
 
@@ -66,10 +71,6 @@ namespace Microsoft.Maui.Hosting
 
 			BuildFontRegistrar(_serviceProvider);
 
-			//we do this here because we can't inject the provider on the App ctor
-			//before we register the user ConfigureServices should this live in IApp ?
-			_app?.SetServiceProvider(_serviceProvider);
-
 			return new AppHost(_serviceProvider, null);
 		}
 
@@ -125,7 +126,6 @@ namespace Microsoft.Maui.Hosting
 		}
 #pragma warning restore CS8714 // The type cannot be used as type parameter in the generic type or method. Nullability of type argument doesn't match 'notnull' constraint
 
-
 		void BuildHostConfiguration()
 		{
 			var configBuilder = new ConfigurationBuilder();
@@ -275,5 +275,10 @@ namespace Microsoft.Maui.Hosting
 		{
 			return ConfigureContainer<TContainerBuilder>(configureDelegate);
 		}
+
+		IHost IHostBuilder.Build()
+		{
+			return Build();
+		}
 	}
-}
+}

src/Core/src/Hosting/AppHostBuilderExtensions.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Maui.Handlers;
+using Microsoft.Maui.Hosting.Internal;
 
 namespace Microsoft.Maui.Hosting
 {
@@ -41,15 +42,15 @@ namespace Microsoft.Maui.Hosting
 				{ typeof(ICheckBox), typeof(CheckBoxHandler) },
 				{ typeof(IEditor), typeof(EditorHandler) },
 				{ typeof(IEntry), typeof(EntryHandler) },
-				{ typeof(ILayout), typeof(LayoutHandler) },
 				{ typeof(ILabel), typeof(LabelHandler) },
+				{ typeof(ILayout), typeof(LayoutHandler) },
 				{ typeof(IPicker), typeof(PickerHandler) },
 				{ typeof(IProgress), typeof(ProgressBarHandler) },
 				{ typeof(ISearchBar), typeof(SearchBarHandler) },
 				{ typeof(ISlider), typeof(SliderHandler) },
 				{ typeof(IStepper), typeof(StepperHandler) },
 				{ typeof(ISwitch), typeof(SwitchHandler) },
-				{ typeof(ITimePicker), typeof(TimePickerHandler) }
+				{ typeof(ITimePicker), typeof(TimePickerHandler) },
 			});
 
 			return builder;
@@ -65,5 +66,31 @@ namespace Microsoft.Maui.Hosting
 			});
 			return builder;
 		}
+
+		public static IAppHostBuilder UseMauiApp<TApp>(this IAppHostBuilder builder)
+			where TApp : MauiApp
+		{
+			builder.ConfigureServices((context, collection) =>
+			{
+				collection.AddSingleton<MauiApp, TApp>();
+			});
+			return builder;
+		}
+
+		public static IAppHostBuilder UseMauiApp<TApp>(this IAppHostBuilder builder, Func<IServiceProvider, TApp> implementationFactory)
+			where TApp : MauiApp
+		{
+			builder.ConfigureServices((context, collection) =>
+			{
+				collection.AddSingleton<MauiApp>(implementationFactory);
+			});
+			return builder;
+		}
+
+		public static IAppHostBuilder UseMauiServiceProviderFactory(this IAppHostBuilder builder, bool constructorInjection)
+		{
+			builder.UseServiceProviderFactory(new MauiServiceProviderFactory(constructorInjection));
+			return builder;
+		}
 	}
-}
+}

src/Core/src/Hosting/AppHostExtensions.cs

@@ -0,0 +1,12 @@
+namespace Microsoft.Maui.Hosting
+{
+	public static class AppHostExtensions
+	{
+		public static void SetServiceProvider(this IAppHost host, App app)
+		{
+			//we do this here because we can't inject the provider on the App ctor
+			//before we register the user ConfigureServices should this live in IApp ?
+			app?.SetServiceProvider(host.Services);
+		}
+	}
+}

src/Core/src/Hosting/IAppHost.cs

@@ -0,0 +1,9 @@
+using Microsoft.Extensions.Hosting;
+
+namespace Microsoft.Maui.Hosting
+{
+	public interface IAppHost : IHost
+	{
+		IMauiHandlersServiceProvider Handlers { get; }
+	}
+}

src/Core/src/Hosting/IAppHostBuilder.cs

@@ -17,6 +17,6 @@ namespace Microsoft.Maui.Hosting
 		new IAppHostBuilder UseServiceProviderFactory<TContainerBuilder>(IServiceProviderFactory<TContainerBuilder> factory);
 		new IAppHostBuilder UseServiceProviderFactory<TContainerBuilder>(Func<HostBuilderContext, IServiceProviderFactory<TContainerBuilder>> factory);
 #pragma warning restore CS8714 // The type cannot be used as type parameter in the generic type or method. Nullability of type argument doesn't match 'notnull' constraint.
-		IHost Build(IApp app);
+		new IAppHost Build();
 	}
-}
+}

src/Core/src/Hosting/Internal/AppHost.cs

@@ -1,23 +1,27 @@
 using System;
 using System.Threading;
 using System.Threading.Tasks;
-using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
 
 namespace Microsoft.Maui.Hosting.Internal
 {
-	internal class AppHost : IHost, IAsyncDisposable
+	internal class AppHost : IAppHost, IAsyncDisposable
 	{
 		readonly ILogger<AppHost>? _logger;
 
 		public AppHost(IServiceProvider services, ILogger<AppHost>? logger)
 		{
 			Services = services ?? throw new ArgumentNullException(nameof(services));
+			Handlers = Services.GetRequiredService<IMauiHandlersServiceProvider>();
+
 			_logger = logger;
 		}
 
 		public IServiceProvider Services { get; }
 
+		public IMauiHandlersServiceProvider Handlers { get; }
+
 		public async Task StartAsync(CancellationToken cancellationToken = default)
 		{
 			_logger?.Starting();
@@ -51,4 +55,4 @@ namespace Microsoft.Maui.Hosting.Internal
 			}
 		}
 	}
-}
+}

src/Core/src/Hosting/Internal/MauiServiceProviderFactory.cs

@@ -5,6 +5,13 @@ namespace Microsoft.Maui.Hosting.Internal
 {
 	internal class MauiServiceProviderFactory : IServiceProviderFactory<IServiceCollection>
 	{
+		readonly bool _constructorInjection;
+
+		public MauiServiceProviderFactory(bool constructorInjection)
+		{
+			_constructorInjection = constructorInjection;
+		}
+
 		public IServiceCollection CreateBuilder(IServiceCollection services)
 		{
 			if (services is IMauiServiceCollection mauiServiceCollection)
@@ -21,10 +28,9 @@ namespace Microsoft.Maui.Hosting.Internal
 		public IServiceProvider CreateServiceProvider(IServiceCollection containerBuilder)
 		{
 			if (containerBuilder is IMauiServiceCollection mauiServiceCollection)
-				return mauiServiceCollection.BuildServiceProvider();
+				return mauiServiceCollection.BuildServiceProvider(_constructorInjection);
 			else
 				throw new InvalidCastException($"{nameof(containerBuilder)} is not {nameof(IMauiServiceCollection)}");
-
 		}
 	}
-}
+}

src/Core/src/Hosting/MauiHandlersServiceProvider.cs

@@ -4,7 +4,8 @@ namespace Microsoft.Maui.Hosting
 {
 	class MauiHandlersServiceProvider : MauiServiceProvider, IMauiHandlersServiceProvider
 	{
-		public MauiHandlersServiceProvider(IMauiServiceCollection collection) : base(collection)
+		public MauiHandlersServiceProvider(IMauiServiceCollection collection)
+			: base(collection, false)
 		{
 		}
 
@@ -14,4 +15,4 @@ namespace Microsoft.Maui.Hosting
 		public IViewHandler? GetHandler<T>() where T : IView
 			=> GetHandler(typeof(T));
 	}
-}
+}

src/Core/src/Hosting/MauiServiceProvider.cs

@@ -1,20 +1,23 @@
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
+using System.Reflection;
 using Microsoft.Extensions.DependencyInjection;
 
 namespace Microsoft.Maui.Hosting
 {
 	class MauiServiceProvider : IMauiServiceProvider
 	{
-		IMauiServiceCollection _collection;
+		readonly IMauiServiceCollection _collection;
+		readonly bool _constructorInjection;
 
 		// TODO: do this properly and support scopes
-		IDictionary<ServiceDescriptor, object?> _singletons;
+		readonly IDictionary<ServiceDescriptor, object?> _singletons;
 
-		public MauiServiceProvider(IMauiServiceCollection collection)
+		public MauiServiceProvider(IMauiServiceCollection collection, bool constructorInjection)
 		{
 			_collection = collection ?? throw new ArgumentNullException(nameof(collection));
+			_constructorInjection = constructorInjection;
 			_singletons = new ConcurrentDictionary<ServiceDescriptor, object?>();
 		}
 
@@ -66,7 +69,12 @@ namespace Microsoft.Maui.Hosting
 		object? CreateInstance(ServiceDescriptor item)
 		{
 			if (item.ImplementationType != null)
-				return Activator.CreateInstance(item.ImplementationType);
+			{
+				if (_constructorInjection)
+					return CreateInstance(item.ImplementationType);
+				else
+					return Activator.CreateInstance(item.ImplementationType);
+			}
 
 			if (item.ImplementationInstance != null)
 				return item.ImplementationInstance;
@@ -76,5 +84,47 @@ namespace Microsoft.Maui.Hosting
 
 			throw new InvalidOperationException($"You need to provide an {nameof(item.ImplementationType)}, an {nameof(item.ImplementationFactory)} or an {nameof(item.ImplementationInstance)}.");
 		}
+
+		object? CreateInstance(Type implementationType)
+		{
+			(ConstructorInfo Constructor, ParameterInfo[] Parameters) match = default;
+			var constructors = implementationType.GetConstructors(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
+			for (var i = 0; i < constructors.Length; i++)
+			{
+				var ctor = constructors[i];
+				if (!ctor.IsFamily && !ctor.IsPrivate)
+				{
+					var parameters = ctor.GetParameters();
+					if (match.Parameters == null || parameters.Length > match.Parameters.Length)
+						match = (ctor, parameters);
+				}
+			}
+
+			if (match.Constructor == null)
+				throw new InvalidOperationException($"The type '{implementationType.Name}' did not have any public or internal constructors.");
+
+			var paramCount = match.Parameters!.Length;
+
+			if (paramCount == 0)
+				return match.Constructor.Invoke(null);
+
+			var paramValues = new object?[paramCount];
+
+			for (var i = 0; i < paramCount; i++)
+			{
+				var param = match.Parameters[i];
+				var value = GetService(param.ParameterType);
+				if (value == null)
+				{
+					if (!param.HasDefaultValue)
+						throw new InvalidOperationException($"No service for type '{param.ParameterType}' has been registered.");
+					else
+						value = param.DefaultValue;
+				}
+				paramValues[i] = value;
+			}
+
+			return match.Constructor.Invoke(paramValues);
+		}
 	}
 }

src/Core/src/Hosting/ServiceProviderExtensions.cs

@@ -4,8 +4,8 @@ namespace Microsoft.Maui.Hosting
 {
 	public static class ServiceProviderExtensions
 	{
-		internal static IServiceProvider BuildServiceProvider(this IMauiServiceCollection serviceCollection)
-			=> new MauiServiceProvider(serviceCollection);
+		internal static IServiceProvider BuildServiceProvider(this IMauiServiceCollection serviceCollection, bool constructorInjection)
+			=> new MauiServiceProvider(serviceCollection, constructorInjection);
 
 		internal static IMauiHandlersServiceProvider BuildHandlersServiceProvider(this IMauiServiceCollection serviceCollection)
 			=> new MauiHandlersServiceProvider(serviceCollection);

src/Core/src/MauiApp.cs

@@ -1,15 +1,19 @@
 using System;
-using System.Collections.Generic;
 
 namespace Microsoft.Maui
 {
 	public abstract class MauiApp : App
 	{
-		public abstract IWindow CreateWindow(IActivationState state);
-
-		public MauiApp()
+		protected MauiApp()
 		{
+			if (Current != null)
+				throw new InvalidOperationException($"Only one {nameof(App)} instance is allowed.");
 
+			Current = this;
 		}
+
+		public static MauiApp? Current { get; internal set; }
+
+		public abstract IWindow CreateWindow(IActivationState state);
 	}
-}
+}

src/Core/src/Platform/Android/HandlerExtensions.cs

@@ -21,8 +21,7 @@ namespace Microsoft.Maui
 				if (handler == null)
 					throw new Exception($"Handler not found for view {view}");
 
-				if (handler is IAndroidViewHandler ahandler)
-					ahandler.SetContext(context.Context);
+				handler.SetMauiContext(context);
 
 				view.Handler = handler;
 			}

src/Core/src/Platform/Android/MauiAppCompatActivity.cs

@@ -21,10 +21,10 @@ namespace Microsoft.Maui
 		{
 			base.OnCreate(savedInstanceState);
 
-			if (App.Current as MauiApp == null)
+			if (MauiApp.Current == null)
 				throw new InvalidOperationException($"App is not {nameof(MauiApp)}");
 
-			var mauiApp = (MauiApp)App.Current;
+			var mauiApp = MauiApp.Current;
 
 			if (mauiApp.Services == null)
 				throw new InvalidOperationException("App was not initialized");
@@ -35,9 +35,6 @@ namespace Microsoft.Maui
 
 			window.MauiContext = mauiContext;
 
-			//Hack for now we set this on the App Static but this should be on IFrameworkElement
-			App.Current.SetHandlerContext(window.MauiContext);
-
 			var content = (window.Page as IView) ??
 				window.Page.View;
 

src/Core/src/Platform/Android/MauiApplication.cs

@@ -2,30 +2,54 @@ using System;
 using Android.Runtime;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
+using Microsoft.Maui.Hosting;
 
 namespace Microsoft.Maui
 {
-	public class MauiApplication<TApplication> : global::Android.App.Application where TApplication : MauiApp
+	public class MauiApplication<TStartup> : Android.App.Application
+		where TStartup : IStartup, new()
 	{
 		public MauiApplication(IntPtr handle, JniHandleOwnership ownerShip) : base(handle, ownerShip)
 		{
-
 		}
-		IHost? _host;
+
 		public override void OnCreate()
 		{
-			if (!(Activator.CreateInstance(typeof(TApplication)) is TApplication app))
-				throw new InvalidOperationException($"We weren't able to create the App {typeof(TApplication)}");
+			var startup = new TStartup();
 
-			_host = app.CreateBuilder().ConfigureServices(ConfigureNativeServices).Build(app);
+			IAppHostBuilder appBuilder;
+
+			if (startup is IHostBuilderStartup hostBuilderStartup)
+			{
+				appBuilder = hostBuilderStartup
+					.CreateHostBuilder();
+			}
+			else
+			{
+				appBuilder = AppHostBuilder
+					.CreateDefaultAppBuilder();
+			}
+
+			appBuilder.
+				ConfigureServices(ConfigureNativeServices);
+
+			startup.Configure(appBuilder);
+
+			var host = appBuilder.Build();
+			if (host.Services == null)
+				throw new InvalidOperationException("App was not intialized");
+
+			var services = host.Services;
+
+			var app = services.GetRequiredService<MauiApp>();
+			host.SetServiceProvider(app);
 
-			//_host.Start();
 			base.OnCreate();
 		}
 
-		//configure native services like HandlersContext, ImageSourceHandlers etc.. 
+		// Configure native services like HandlersContext, ImageSourceHandlers etc.. 
 		void ConfigureNativeServices(HostBuilderContext ctx, IServiceCollection services)
 		{
 		}
 	}
-}
+}

src/Core/src/Platform/iOS/HandlerExtensions.cs

@@ -20,6 +20,8 @@ namespace Microsoft.Maui
 				if (handler == null)
 					throw new Exception($"Handler not found for view {view}");
 
+				handler.SetMauiContext(context);
+
 				view.Handler = handler;
 			}
 

src/Core/src/Platform/iOS/MauiUIApplicationDelegate.cs

@@ -1,6 +1,4 @@
 using System;
-using System.Collections.Generic;
-using System.Text;
 using Foundation;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
@@ -9,7 +7,8 @@ using UIKit;
 
 namespace Microsoft.Maui
 {
-	public class MauiUIApplicationDelegate<TApplication> : UIApplicationDelegate, IUIApplicationDelegate where TApplication : MauiApp
+	public class MauiUIApplicationDelegate<TStartup> : UIApplicationDelegate, IUIApplicationDelegate
+		where TStartup : IStartup, new()
 	{
 		public override UIWindow? Window
 		{
@@ -19,23 +18,40 @@ namespace Microsoft.Maui
 
 		public override bool FinishedLaunching(UIApplication application, NSDictionary launchOptions)
 		{
-			if (!(Activator.CreateInstance(typeof(TApplication)) is TApplication app))
-				throw new InvalidOperationException($"We weren't able to create the App {typeof(TApplication)}");
+			var startup = new TStartup();
 
-			var host = app.CreateBuilder().ConfigureServices(ConfigureNativeServices).Build(app);
+			IAppHostBuilder appBuilder;
 
-			if (MauiApp.Current == null || MauiApp.Current.Services == null)
+			if (startup is IHostBuilderStartup hostBuilderStartup)
+			{
+				appBuilder = hostBuilderStartup
+					.CreateHostBuilder();
+			}
+			else
+			{
+				appBuilder = AppHostBuilder
+					.CreateDefaultAppBuilder();
+			}
+
+			appBuilder.
+				ConfigureServices(ConfigureNativeServices);
+
+			startup.Configure(appBuilder);
+
+			var host = appBuilder.Build();
+			if (host.Services == null)
 				throw new InvalidOperationException("App was not intialized");
 
+			var services = host.Services;
 
-			var mauiContext = new MauiContext(MauiApp.Current.Services);
+			var app = services.GetRequiredService<MauiApp>();
+			host.SetServiceProvider(app);
+
+			var mauiContext = new MauiContext(services);
 			var window = app.CreateWindow(new ActivationState(mauiContext));
 
 			window.MauiContext = mauiContext;
 
-			//Hack for now we set this on the App Static but this should be on IFrameworkElement
-			App.Current.SetHandlerContext(window.MauiContext);
-
 			var content = (window.Page as IView) ?? window.Page.View;
 
 			Window = new UIWindow
@@ -53,7 +69,6 @@ namespace Microsoft.Maui
 
 		void ConfigureNativeServices(HostBuilderContext ctx, IServiceCollection services)
 		{
-
 		}
 	}
-}
+}

src/Core/tests/Benchmarks/Benchmarks/GetHandlersBenchmarker.cs

@@ -6,7 +6,7 @@ namespace Microsoft.Maui.Handlers.Benchmarks
 	[MemoryDiagnoser]
 	public class GetHandlersBenchmarker
 	{
-		MockApp _app;
+		IAppHost _host;
 
 		Registrar<IFrameworkElement, IViewHandler> _registrar;
 
@@ -16,10 +16,9 @@ namespace Microsoft.Maui.Handlers.Benchmarks
 		[GlobalSetup(Target = nameof(GetHandlerUsingDI))]
 		public void SetupForDI()
 		{
-			_app = new MockApp();
-			_app.CreateBuilder()
-				.RegisterHandler<IButton, ButtonHandler>()
-				.Build(_app);
+			_host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.Build();
 		}
 
 		[GlobalSetup(Target = nameof(GetHandlerUsingRegistrar))]
@@ -34,7 +33,7 @@ namespace Microsoft.Maui.Handlers.Benchmarks
 		{
 			for (int i = 0; i < N; i++)
 			{
-				_app.Context.Handlers.GetHandler<IButton>();
+				_host.Handlers.GetHandler<IButton>();
 			}
 		}
 
@@ -47,4 +46,4 @@ namespace Microsoft.Maui.Handlers.Benchmarks
 			}
 		}
 	}
-}
+}

src/Core/tests/Benchmarks/Benchmarks/MauiServiceProviderBenchmarker.cs

@@ -0,0 +1,176 @@
+using System;
+using BenchmarkDotNet.Attributes;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyInjection.Extensions;
+using Microsoft.Maui.Hosting;
+
+namespace Microsoft.Maui.Handlers.Benchmarks
+{
+	[MemoryDiagnoser]
+	public class MauiServiceProviderBenchmarker
+	{
+		IAppHost _host;
+
+		[Params(100_000)]
+		public int N { get; set; }
+
+		[IterationSetup(Target = nameof(DefaultBuilder))]
+		public void SetupForDefaultBuilder()
+		{
+			_host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.ConfigureServices((ctx, svc) => svc.AddTransient<IFooService, FooService>())
+				.Build();
+		}
+
+		[IterationSetup(Target = nameof(DefaultBuilderWithConstructorInjection))]
+		public void SetupForDefaultBuilderWithConstructorInjection()
+		{
+			_host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.UseMauiServiceProviderFactory(true)
+				.ConfigureServices((ctx, svc) => svc.AddTransient<IFooService, FooService>())
+				.Build();
+		}
+
+		[IterationSetup(Target = nameof(OneConstructorParameter))]
+		public void SetupForOneConstructorParameter()
+		{
+			_host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.UseMauiServiceProviderFactory(true)
+				.ConfigureServices((ctx, svc) =>
+				{
+					svc.AddTransient<IFooService, FooService>();
+					svc.AddTransient<IFooBarService, FooBarWithFooService>();
+				})
+				.Build();
+		}
+
+		[IterationSetup(Target = nameof(TwoConstructorParameters))]
+		public void SetupForTwoConstructorParameters()
+		{
+			_host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.UseMauiServiceProviderFactory(true)
+				.ConfigureServices((ctx, svc) =>
+				{
+					svc.AddTransient<IFooService, FooService>();
+					svc.AddTransient<IBarService, BarService>();
+					svc.AddTransient<IFooBarService, FooBarWithFooAndBarService>();
+				})
+				.Build();
+		}
+
+		[IterationSetup(Target = nameof(ExtensionsWithConstructorInjection))]
+		public void SetupForExtensionsWithConstructorInjection()
+		{
+			_host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.UseServiceProviderFactory(new DIExtensionsServiceProviderFactory())
+				.ConfigureServices((ctx, svc) => svc.AddTransient<IFooService, FooService>())
+				.Build();
+		}
+
+		[IterationSetup(Target = nameof(ExtensionsWithOneConstructorParameter))]
+		public void SetupForExtensionsWithOneConstructorParameter()
+		{
+			_host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.UseServiceProviderFactory(new DIExtensionsServiceProviderFactory())
+				.ConfigureServices((ctx, svc) =>
+				{
+					svc.AddTransient<IFooService, FooService>();
+					svc.AddTransient<IFooBarService, FooBarWithFooService>();
+				})
+				.Build();
+		}
+
+		[IterationSetup(Target = nameof(ExtensionsWithTwoConstructorParameters))]
+		public void SetupForExtensionsWithTwoConstructorParameters()
+		{
+			_host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.UseServiceProviderFactory(new DIExtensionsServiceProviderFactory())
+				.ConfigureServices((ctx, svc) =>
+				{
+					svc.AddTransient<IFooService, FooService>();
+					svc.AddTransient<IBarService, BarService>();
+					svc.AddTransient<IFooBarService, FooBarWithFooAndBarService>();
+				})
+				.Build();
+		}
+
+		[Benchmark(Baseline = true)]
+		public void DefaultBuilder()
+		{
+			for (int i = 0; i < N; i++)
+			{
+				_host.Services.GetService<IFooService>();
+			}
+		}
+
+		[Benchmark]
+		public void DefaultBuilderWithConstructorInjection()
+		{
+			for (int i = 0; i < N; i++)
+			{
+				_host.Services.GetService<IFooService>();
+			}
+		}
+
+		[Benchmark]
+		public void OneConstructorParameter()
+		{
+			for (int i = 0; i < N; i++)
+			{
+				_host.Services.GetService<IFooBarService>();
+			}
+		}
+
+		[Benchmark]
+		public void TwoConstructorParameters()
+		{
+			for (int i = 0; i < N; i++)
+			{
+				_host.Services.GetService<IFooBarService>();
+			}
+		}
+
+		[Benchmark]
+		public void ExtensionsWithConstructorInjection()
+		{
+			for (int i = 0; i < N; i++)
+			{
+				_host.Services.GetService<IFooService>();
+			}
+		}
+
+		[Benchmark]
+		public void ExtensionsWithOneConstructorParameter()
+		{
+			for (int i = 0; i < N; i++)
+			{
+				_host.Services.GetService<IFooBarService>();
+			}
+		}
+
+		[Benchmark]
+		public void ExtensionsWithTwoConstructorParameters()
+		{
+			for (int i = 0; i < N; i++)
+			{
+				_host.Services.GetService<IFooBarService>();
+			}
+		}
+
+		public class DIExtensionsServiceProviderFactory : IServiceProviderFactory<ServiceCollection>
+		{
+			public ServiceCollection CreateBuilder(IServiceCollection services)
+				=> new ServiceCollection { services };
+
+			public IServiceProvider CreateServiceProvider(ServiceCollection containerBuilder)
+				=> containerBuilder.BuildServiceProvider();
+		}
+	}
+}

src/Core/tests/Benchmarks/Core.Benchmarks.csproj

@@ -13,6 +13,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="BenchmarkDotNet" Version="0.12.1" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" />
   </ItemGroup>
 
   <ItemGroup>

src/Core/tests/Benchmarks/Program.cs

@@ -6,7 +6,8 @@ namespace Microsoft.Maui.Handlers.Benchmarks
 	{
 		static void Main(string[] args)
 		{
+			//BenchmarkRunner.Run<MauiServiceProviderBenchmarker>();
 			BenchmarkSwitcher.FromAssembly(typeof(Program).Assembly).RunAllJoined();
 		}
 	}
-}
+}

src/Core/tests/Benchmarks/Stubs/AppStub.cs

@@ -1,20 +1,10 @@
-using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.Hosting;
-using Microsoft.Maui.Hosting;
-
 namespace Microsoft.Maui.Handlers.Benchmarks
 {
-	class MockApp : App
+	class AppStub : MauiApp
 	{
-		public override IAppHostBuilder CreateBuilder()
+		public override IWindow CreateWindow(IActivationState state)
 		{
-			return base.CreateBuilder()
-				.ConfigureServices(ConfigureNativeServices);
-		}
-
-		void ConfigureNativeServices(HostBuilderContext ctx, IServiceCollection services)
-		{
-			services.AddSingleton<IMauiContext>(provider => new HandlersContextStub(provider));
+			return new WindowStub();
 		}
 	}
-}
+}

src/Core/tests/Benchmarks/Stubs/TestServices.cs

@@ -0,0 +1,82 @@
+namespace Microsoft.Maui.Handlers.Benchmarks
+{
+	interface IFooService
+	{
+	}
+
+	interface IBarService
+	{
+	}
+
+	interface IFooBarService
+	{
+	}
+
+	class FooService : IFooService
+	{
+	}
+
+	class BarService : IBarService
+	{
+	}
+
+	class FooBarWithFooService : IFooBarService
+	{
+		public FooBarWithFooService(IFooService foo)
+		{
+			Foo = foo;
+		}
+
+		public IFooService Foo { get; }
+	}
+
+	class FooBarWithFooAndBarService : IFooBarService
+	{
+		public FooBarWithFooAndBarService(IFooService foo, IBarService bar)
+		{
+			Foo = foo;
+			Bar = bar;
+		}
+
+		public IFooService Foo { get; }
+
+		public IBarService Bar { get; }
+	}
+
+	class FooDualConstructor : IFooBarService
+	{
+		public FooDualConstructor(IFooService foo)
+		{
+			Foo = foo;
+		}
+
+		public FooDualConstructor(IBarService bar)
+		{
+			Bar = bar;
+		}
+
+		public IFooService Foo { get; }
+
+		public IBarService Bar { get; }
+	}
+
+	class FooDefaultValueConstructor : IFooBarService
+	{
+		public FooDefaultValueConstructor(IBarService bar = null)
+		{
+			Bar = bar;
+		}
+
+		public IBarService Bar { get; }
+	}
+
+	class FooDefaultSystemValueConstructor : IFooBarService
+	{
+		public FooDefaultSystemValueConstructor(string text = "Default Value")
+		{
+			Text = text;
+		}
+
+		public string Text { get; }
+	}
+}

src/Core/tests/Benchmarks/Stubs/WindowStub.cs

@@ -0,0 +1,10 @@
+using System;
+
+namespace Microsoft.Maui.Handlers.Benchmarks
+{
+	public class WindowStub : IWindow
+	{
+		public IMauiContext MauiContext { get; set; }
+		public IPage Page { get; set; }
+	}
+}

src/Core/tests/DeviceTests/Handlers/ActivityIndicator/ActivityIndicatorHandlerTests.cs

@@ -8,10 +8,6 @@ namespace Microsoft.Maui.DeviceTests
 	[Category(TestCategory.ActivityIndicator)]
 	public partial class ActivityIndicatorHandlerTests : HandlerTestBase<ActivityIndicatorHandler, ActivityIndicatorStub>
 	{
-		public ActivityIndicatorHandlerTests(HandlerTestFixture fixture) : base(fixture)
-		{
-		}
-
 		[Theory(DisplayName = "IsRunning Initializes Correctly")]
 		[InlineData(true)]
 		[InlineData(false)]

src/Core/tests/DeviceTests/Handlers/Button/ButtonHandlerTests.cs

@@ -9,10 +9,6 @@ namespace Microsoft.Maui.DeviceTests
 	[Category(TestCategory.Button)]
 	public partial class ButtonHandlerTests : HandlerTestBase<ButtonHandler, ButtonStub>
 	{
-		public ButtonHandlerTests(HandlerTestFixture fixture) : base(fixture)
-		{
-		}
-
 		[Fact(DisplayName = "Text Initializes Correctly")]
 		public async Task TextInitializesCorrectly()
 		{

src/Core/tests/DeviceTests/Handlers/CheckBox/CheckBoxHandlerTests.cs

@@ -8,10 +8,6 @@ namespace Microsoft.Maui.DeviceTests
 	[Category(TestCategory.CheckBox)]
 	public partial class CheckBoxHandlerTests : HandlerTestBase<CheckBoxHandler, CheckBoxStub>
 	{
-		public CheckBoxHandlerTests(HandlerTestFixture fixture) : base(fixture)
-		{
-		}
-
 		[Theory(DisplayName = "IsChecked Initializes Correctly")]
 		[InlineData(true)]
 		[InlineData(false)]

src/Core/tests/DeviceTests/Handlers/Editor/EditorHandlerTests.cs

@@ -9,10 +9,6 @@ namespace Microsoft.Maui.DeviceTests
 	[Category(TestCategory.Editor)]
 	public partial class EditorHandlerTests : HandlerTestBase<EditorHandler, EditorStub>
 	{
-		public EditorHandlerTests(HandlerTestFixture fixture) : base(fixture)
-		{
-		}
-
 		[Fact(DisplayName = "Text Initializes Correctly")]
 		public async Task TextInitializesCorrectly()
 		{

src/Core/tests/DeviceTests/Handlers/Entry/EntryHandlerTests.cs

@@ -9,10 +9,6 @@ namespace Microsoft.Maui.DeviceTests
 	[Category(TestCategory.Entry)]
 	public partial class EntryHandlerTests : HandlerTestBase<EntryHandler, EntryStub>
 	{
-		public EntryHandlerTests(HandlerTestFixture fixture) : base(fixture)
-		{
-		}
-
 		[Fact(DisplayName = "Text Initializes Correctly")]
 		public async Task TextInitializesCorrectly()
 		{

src/Core/tests/DeviceTests/Handlers/HandlerTestBase.Android.cs

@@ -8,8 +8,7 @@ namespace Microsoft.Maui.DeviceTests
 		protected THandler CreateHandler(IView view)
 		{
 			var handler = Activator.CreateInstance<THandler>();
-			if (handler is IAndroidViewHandler av)
-				av.SetContext(DefaultContext);
+			handler.SetMauiContext(MauiContext);
 
 			handler.SetVirtualView(view);
 			view.Handler = handler;

src/Core/tests/DeviceTests/Handlers/HandlerTestBase.cs

@@ -2,23 +2,48 @@ using System;
 using System.Threading.Tasks;
 using Microsoft.Maui.DeviceTests.Stubs;
 using Microsoft.Maui.Essentials;
+using Microsoft.Maui.Hosting;
 using Xunit;
 
 namespace Microsoft.Maui.DeviceTests
 {
-	[Collection(TestCollections.Handlers)]
-	public partial class HandlerTestBase<THandler, TStub> : TestBase
+	public partial class HandlerTestBase<THandler, TStub> : TestBase, IDisposable
 		where THandler : IViewHandler
 		where TStub : StubBase, IView, new()
 	{
-		readonly HandlerTestFixture _fixture;
+		AppStub _app;
+		IAppHost _host;
+		IMauiContext _context;
 
-		public HandlerTestBase(HandlerTestFixture fixture)
+		public HandlerTestBase()
 		{
-			_fixture = fixture;
+			var appBuilder = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.ConfigureFonts((ctx, fonts) =>
+				{
+					fonts.AddFont("dokdo_regular.ttf", "Dokdo");
+				});
+
+			_host = appBuilder.Build();
+
+			_app = new AppStub();
+
+			_host.SetServiceProvider(_app);
+
+			_context = new ContextStub(_host.Services);
 		}
 
-		public IApp App => _fixture.App;
+		public void Dispose()
+		{
+			_host.Dispose();
+			_host = null;
+			_app = null;
+			_context = null;
+		}
+
+		public IApp App => _app;
+
+		public IMauiContext MauiContext => _context;
 
 		public Task<T> InvokeOnMainThreadAsync<T>(Func<T> func) =>
 			MainThread.InvokeOnMainThreadAsync(func);

src/Core/tests/DeviceTests/Handlers/HandlerTestBase.iOS.cs

@@ -11,6 +11,8 @@ namespace Microsoft.Maui.DeviceTests
 		protected THandler CreateHandler(IView view)
 		{
 			var handler = Activator.CreateInstance<THandler>();
+			handler.SetMauiContext(MauiContext);
+
 			handler.SetVirtualView(view);
 			view.Handler = handler;
 

src/Core/tests/DeviceTests/Handlers/HandlerTestCollection.cs

@@ -1,9 +0,0 @@
-using Xunit;
-
-namespace Microsoft.Maui.DeviceTests
-{
-	[CollectionDefinition(TestCollections.Handlers)]
-	public class HandlerTestCollection : ICollectionFixture<HandlerTestFixture>
-	{
-	}
-}

src/Core/tests/DeviceTests/Handlers/HandlerTestFixture.cs

@@ -1,45 +0,0 @@
-using System;
-using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.Hosting;
-using Microsoft.Maui.DeviceTests.Stubs;
-using Microsoft.Maui.Hosting;
-
-namespace Microsoft.Maui.DeviceTests
-{
-	public class HandlerTestFixture : IDisposable
-	{
-		AppStub _app;
-		IHost _host;
-		IMauiContext _context;
-
-		public HandlerTestFixture()
-		{
-			_app = new AppStub();
-			_context = new ContextStub(_app);
-			_host = _app
-				.CreateBuilder()
-				.ConfigureFonts((ctx, fonts) =>
-				{
-					fonts.AddFont("dokdo_regular.ttf", "Dokdo");
-				})
-				.ConfigureServices((ctx, services) =>
-				{
-					services.AddSingleton(_context);
-				})
-				.Build(_app);
-		}
-
-		public void Dispose()
-		{
-			_host.Dispose();
-			_host = null;
-
-			_app.Dispose();
-			_app = null;
-
-			_context = null;
-		}
-
-		public IApp App => _app;
-	}
-}

src/Core/tests/DeviceTests/Handlers/Label/LabelHandlerTests.cs

@@ -9,10 +9,6 @@ namespace Microsoft.Maui.DeviceTests
 	[Category(TestCategory.Label)]
 	public partial class LabelHandlerTests : HandlerTestBase<LabelHandler, LabelStub>
 	{
-		public LabelHandlerTests(HandlerTestFixture fixture) : base(fixture)
-		{
-		}
-
 		[Fact(DisplayName = "Background Color Initializes Correctly")]
 		public async Task BackgroundColorInitializesCorrectly()
 		{

src/Core/tests/DeviceTests/Handlers/Layout/LayoutHandlerTests.cs

@@ -9,10 +9,6 @@ namespace Microsoft.Maui.DeviceTests.Handlers.Layout
 	[Category(TestCategory.Layout)]
 	public partial class LayoutHandlerTests : HandlerTestBase<LayoutHandler, LayoutStub>
 	{
-		public LayoutHandlerTests(HandlerTestFixture fixture) : base(fixture)
-		{
-		}
-
 		[Fact(DisplayName = "Empty layout")]
 		public async Task EmptyLayout()
 		{

src/Core/tests/DeviceTests/Handlers/Picker/PickerHandlerTests.cs

@@ -6,8 +6,5 @@ namespace Microsoft.Maui.DeviceTests
 	[Category(TestCategory.Picker)]
 	public partial class PickerHandlerTests : HandlerTestBase<PickerHandler, PickerStub>
 	{
-		public PickerHandlerTests(HandlerTestFixture fixture) : base(fixture)
-		{
-		}
 	}
 }

src/Core/tests/DeviceTests/Handlers/ProgressBar/ProgressBarTests.cs

@@ -9,10 +9,6 @@ namespace Microsoft.Maui.DeviceTests
 	[Category("ProgressBarHandler")]
 	public partial class ProgressBarHandlerTests : HandlerTestBase<ProgressBarHandler, ProgressBarStub>
 	{
-		public ProgressBarHandlerTests(HandlerTestFixture fixture) : base(fixture)
-		{
-		}
-
 		[Theory(DisplayName = "Progress Initializes Correctly")]
 		[InlineData(0.25)]
 		[InlineData(0.5)]

src/Core/tests/DeviceTests/Handlers/SearchBar/SearchBarHandlerTests.cs

@@ -8,10 +8,6 @@ namespace Microsoft.Maui.DeviceTests
 	[Category(TestCategory.SearchBar)]
 	public partial class SearchBarHandlerTests : HandlerTestBase<SearchBarHandler, SearchBarStub>
 	{
-		public SearchBarHandlerTests(HandlerTestFixture fixture) : base(fixture)
-		{
-		}
-
 		[Fact(DisplayName = "Text Initializes Correctly")]
 		public async Task TextInitializesCorrectly()
 		{

src/Core/tests/DeviceTests/Handlers/Slider/SliderHandlerTests.cs

@@ -9,10 +9,6 @@ namespace Microsoft.Maui.DeviceTests
 	[Category(TestCategory.Slider)]
 	public partial class SliderHandlerTests : HandlerTestBase<SliderHandler, SliderStub>
 	{
-		public SliderHandlerTests(HandlerTestFixture fixture) : base(fixture)
-		{
-		}
-
 		[Theory(DisplayName = "Percent Value Initializes Correctly")]
 		[InlineData(0, 1, 0)]
 		[InlineData(0, 1, 0.5)]

src/Core/tests/DeviceTests/Handlers/Stepper/StepperHandlerTests.cs

@@ -8,10 +8,6 @@ namespace Microsoft.Maui.DeviceTests
 	[Category(TestCategory.Stepper)]
 	public partial class StepperHandlerTests : HandlerTestBase<StepperHandler, StepperStub>
 	{
-		public StepperHandlerTests(HandlerTestFixture fixture) : base(fixture)
-		{
-		}
-
 		[Fact(DisplayName = "Is Value Initializes Correctly")]
 		public async Task ValueInitializesCorrectly()
 		{

src/Core/tests/DeviceTests/Handlers/Switch/SwitchHandlerTests.cs

@@ -9,10 +9,6 @@ namespace Microsoft.Maui.DeviceTests
 	[Category(TestCategory.Switch)]
 	public partial class SwitchHandlerTests : HandlerTestBase<SwitchHandler, SwitchStub>
 	{
-		public SwitchHandlerTests(HandlerTestFixture fixture) : base(fixture)
-		{
-		}
-
 		[Fact(DisplayName = "Is Toggled Initializes Correctly")]
 		public async Task IsToggledInitializesCorrectly()
 		{

src/Core/tests/DeviceTests/Handlers/TimePicker/TimePickerHandlerTests.cs

@@ -8,10 +8,6 @@ namespace Microsoft.Maui.DeviceTests
 	[Category(TestCategory.TimePicker)]
 	public partial class TimePickerHandlerTests : HandlerTestBase<TimePickerHandler, TimePickerStub>
 	{
-		public TimePickerHandlerTests(HandlerTestFixture fixture) : base(fixture)
-		{
-		}
-
 		[Fact(DisplayName = "Time Initializes Correctly")]
 		public async Task IsToggledInitializesCorrectly()
 		{
@@ -22,4 +18,4 @@ namespace Microsoft.Maui.DeviceTests
 			await ValidateTime(timePickerStub, () => timePickerStub.Time = time);
 		}
 	}
-}
+}

src/Core/tests/DeviceTests/Stubs/AppStub.cs

@@ -1,17 +1,6 @@
-using System;
-
 namespace Microsoft.Maui.DeviceTests.Stubs
 {
-	class AppStub : MauiApp, IDisposable
+	class AppStub : App
 	{
-		public override IWindow CreateWindow(IActivationState state)
-		{
-			throw new NotImplementedException();
-		}
-
-		public void Dispose()
-		{
-			Current = null;
-		}
 	}
 }

src/Core/tests/DeviceTests/Stubs/ContextStub.cs

@@ -3,29 +3,20 @@ using Microsoft.Extensions.DependencyInjection;
 
 namespace Microsoft.Maui.DeviceTests.Stubs
 {
-	class ContextStub : IMauiContext, IDisposable
+	class ContextStub : IMauiContext
 	{
-		AppStub _app;
-
-		public ContextStub(AppStub app)
+		public ContextStub(IServiceProvider services)
 		{
-			_app = app;
+			Services = services;
 		}
 
-		public IServiceProvider Services =>
-			_app.Services;
+		public IServiceProvider Services { get; }
 
 		public IMauiHandlersServiceProvider Handlers =>
 			Services.GetRequiredService<IMauiHandlersServiceProvider>();
 
 #if __ANDROID__
-		public Android.Content.Context Context =>
-			Android.App.Application.Context;
+		public Android.Content.Context Context => Platform.DefaultContext;
 #endif
-
-		public void Dispose()
-		{
-			_app = null;
-		}
 	}
 }

src/Core/tests/UnitTests/HostBuilderHandlerTests.cs

@@ -0,0 +1,113 @@
+using System;
+using System.Collections.Generic;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Maui.Handlers;
+using Microsoft.Maui.Hosting;
+using Microsoft.Maui.Tests;
+using Xunit;
+
+namespace Microsoft.Maui.UnitTests
+{
+	[Category(TestCategory.Core, TestCategory.Hosting)]
+	public class HostBuilderHandlerTests
+	{
+		[Fact]
+		public void CanBuildAHost()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.Build();
+
+			Assert.NotNull(host);
+		}
+
+		[Fact]
+		public void CanGetIMauiHandlersServiceProviderFromServices()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.Build();
+
+			Assert.NotNull(host);
+			Assert.NotNull(host.Services);
+			Assert.NotNull(host.Handlers);
+			Assert.IsType<MauiHandlersServiceProvider>(host.Handlers);
+			Assert.Equal(host.Handlers, host.Services.GetService<IMauiHandlersServiceProvider>());
+		}
+
+		[Fact]
+		public void CanRegisterAndGetHandler()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.RegisterHandler<IViewStub, ViewHandlerStub>()
+				.Build();
+
+			var handler = host.Handlers.GetHandler(typeof(IViewStub));
+
+			Assert.NotNull(handler);
+			Assert.IsType<ViewHandlerStub>(handler);
+		}
+
+		[Fact]
+		public void CanRegisterAndGetHandlerWithDictionary()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.RegisterHandlers(new Dictionary<Type, Type>
+				{
+					{ typeof(IViewStub), typeof(ViewHandlerStub) }
+				})
+				.Build();
+
+			var handler = host.Handlers.GetHandler(typeof(IViewStub));
+
+			Assert.NotNull(handler);
+			Assert.IsType<ViewHandlerStub>(handler);
+		}
+
+		[Fact]
+		public void CanRegisterAndGetHandlerForType()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.RegisterHandler<IViewStub, ViewHandlerStub>()
+				.Build();
+
+			var handler = host.Handlers.GetHandler(typeof(ViewStub));
+
+			Assert.NotNull(handler);
+			Assert.IsType<ViewHandlerStub>(handler);
+		}
+
+		[Fact]
+		public void DefaultHandlersAreRegistered()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.Build();
+
+			var handler = host.Handlers.GetHandler(typeof(IButton));
+
+			Assert.NotNull(handler);
+			Assert.IsType<ButtonHandler>(handler);
+		}
+
+		[Fact]
+		public void CanSpecifyHandler()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.RegisterHandler<ButtonStub, ButtonHandlerStub>()
+				.Build();
+
+			var defaultHandler = host.Handlers.GetHandler(typeof(IButton));
+			var specificHandler = host.Handlers.GetHandler(typeof(ButtonStub));
+
+			Assert.NotNull(defaultHandler);
+			Assert.NotNull(specificHandler);
+			Assert.IsType<ButtonHandler>(defaultHandler);
+			Assert.IsType<ButtonHandlerStub>(specificHandler);
+		}
+	}
+}

src/Core/tests/UnitTests/HostBuilderServicesTests.cs

@@ -0,0 +1,202 @@
+using System;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Maui.Hosting;
+using Microsoft.Maui.Tests;
+using Xunit;
+
+namespace Microsoft.Maui.UnitTests
+{
+	[Category(TestCategory.Core, TestCategory.Hosting)]
+	public class HostBuilderServicesTests
+	{
+		[Fact]
+		public void CanGetServices()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.Build();
+
+			Assert.NotNull(host);
+			Assert.NotNull(host.Services);
+		}
+
+		[Fact]
+		public void GetServiceThrowsWhenConstructorParamTypesWereNotRegistered()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.UseMauiServiceProviderFactory(true)
+				.ConfigureServices((ctx, services) => services.AddTransient<IFooBarService, FooBarService>())
+				.Build();
+
+			Assert.Throws<InvalidOperationException>(() => host.Services.GetService<IFooBarService>());
+		}
+
+		[Fact]
+		public void GetServiceThrowsOnMultipleConstructors()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.UseMauiServiceProviderFactory(true)
+				.ConfigureServices((ctx, services) => services.AddTransient<IFooBarService, FooDualConstructor>())
+				.Build();
+
+			var ex = Assert.Throws<InvalidOperationException>(() => host.Services.GetService<IFooBarService>());
+
+			Assert.Contains("IFooService", ex.Message);
+		}
+
+		[Fact]
+		public void GetServiceCanReturnTypesThatHaveConstructorParams()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.UseMauiServiceProviderFactory(true)
+				.ConfigureServices((ctx, services) =>
+				{
+					services.AddTransient<IFooService, FooService>();
+					services.AddTransient<IBarService, BarService>();
+					services.AddTransient<IFooBarService, FooBarService>();
+				})
+				.Build();
+
+			var foobar = host.Services.GetService<IFooBarService>();
+
+			Assert.NotNull(foobar);
+			Assert.IsType<FooBarService>(foobar);
+		}
+
+		[Fact]
+		public void GetServiceCanReturnTypesThatHaveUnregisteredConstructorParamsButHaveDefaultValues()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.UseMauiServiceProviderFactory(true)
+				.ConfigureServices((ctx, services) =>
+				{
+					services.AddTransient<IFooBarService, FooDefaultValueConstructor>();
+				})
+				.Build();
+
+			var foo = host.Services.GetService<IFooBarService>();
+
+			Assert.NotNull(foo);
+
+			var actual = Assert.IsType<FooDefaultValueConstructor>(foo);
+
+			Assert.Null(actual.Bar);
+		}
+
+		[Fact]
+		public void GetServiceCanReturnTypesThatHaveRegisteredConstructorParamsAndHaveDefaultValues()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.UseMauiServiceProviderFactory(true)
+				.ConfigureServices((ctx, services) =>
+				{
+					services.AddTransient<IBarService, BarService>();
+					services.AddTransient<IFooBarService, FooDefaultValueConstructor>();
+				})
+				.Build();
+
+			var foo = host.Services.GetService<IFooBarService>();
+
+			Assert.NotNull(foo);
+
+			var actual = Assert.IsType<FooDefaultValueConstructor>(foo);
+
+			Assert.NotNull(actual.Bar);
+			Assert.IsType<BarService>(actual.Bar);
+		}
+
+		[Fact]
+		public void GetServiceCanReturnTypesThatHaveSystemDefaultValues()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.UseMauiServiceProviderFactory(true)
+				.ConfigureServices((ctx, services) =>
+				{
+					services.AddTransient<IFooBarService, FooDefaultSystemValueConstructor>();
+				})
+				.Build();
+
+			var foo = host.Services.GetService<IFooBarService>();
+
+			Assert.NotNull(foo);
+
+			var actual = Assert.IsType<FooDefaultSystemValueConstructor>(foo);
+
+			Assert.Equal("Default Value", actual.Text);
+		}
+
+		[Fact]
+		public void WillRetrieveDifferentTransientServices()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.ConfigureServices((ctx, services) => services.AddTransient<IFooService, FooService>())
+				.Build();
+
+			AssertTransient<IFooService, FooService>(host.Services);
+		}
+
+		[Fact]
+		public void WillRetrieveSameSingletonServices()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.ConfigureServices((ctx, services) => services.AddSingleton<IFooService, FooService>())
+				.Build();
+
+			AssertSingleton<IFooService, FooService>(host.Services);
+		}
+
+		[Fact]
+		public void WillRetrieveMixedServices()
+		{
+			var host = AppHostBuilder
+				.CreateDefaultAppBuilder()
+				.ConfigureServices((ctx, services) =>
+				{
+					services.AddSingleton<IFooService, FooService>();
+					services.AddTransient<IBarService, BarService>();
+				})
+				.Build();
+
+			AssertSingleton<IFooService, FooService>(host.Services);
+			AssertTransient<IBarService, BarService>(host.Services);
+		}
+
+		static void AssertTransient<TInterface, TConcrete>(IServiceProvider services)
+		{
+			var service1 = services.GetService<TInterface>();
+
+			Assert.NotNull(service1);
+			Assert.IsType<TConcrete>(service1);
+
+			var service2 = services.GetService<TInterface>();
+
+			Assert.NotNull(service2);
+			Assert.IsType<TConcrete>(service2);
+
+			Assert.NotEqual(service1, service2);
+		}
+
+		static void AssertSingleton<TInterface, TConcrete>(IServiceProvider services)
+		{
+			var service1 = services.GetService<TInterface>();
+
+			Assert.NotNull(service1);
+			Assert.IsType<TConcrete>(service1);
+
+			var service2 = services.GetService<TInterface>();
+
+			Assert.NotNull(service2);
+			Assert.IsType<TConcrete>(service2);
+
+			Assert.Equal(service1, service2);
+		}
+	}
+}

src/Core/tests/UnitTests/HostBuilderTests.cs

@@ -1,232 +0,0 @@
-using System;
-using System.Collections.Generic;
-using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Maui.Handlers;
-using Microsoft.Maui.Hosting;
-using Microsoft.Maui.Tests;
-using Xunit;
-
-namespace Microsoft.Maui.UnitTests
-{
-	[Category(TestCategory.Core, TestCategory.Hosting)]
-	public partial class HostBuilderTests : IDisposable
-	{
-		[Fact]
-		public void CanBuildAHost()
-		{
-			var host = App.CreateDefaultBuilder().Build();
-			Assert.NotNull(host);
-		}
-
-		[Fact]
-		public void CanGetStaticApp()
-		{
-			var app = new AppStub();
-			app.CreateBuilder().Build(app);
-
-			Assert.NotNull(MauiApp.Current);
-			Assert.Equal(MauiApp.Current, app);
-		}
-
-		[Fact]
-		public void ShouldntCreateMultipleApp()
-		{
-			var app = new AppStub();
-			Assert.Throws<InvalidOperationException>(() => new AppStub());
-		}
-
-		[Fact]
-		public void CanGetServices()
-		{
-			var app = new AppStub();
-			app.CreateBuilder().Build(app);
-
-			Assert.NotNull(app.Services);
-		}
-
-		[Fact]
-		public void CanGetStaticServices()
-		{
-			var app = new AppStub();
-			app.CreateBuilder().Build(app);
-
-			Assert.NotNull(MauiApp.Current.Services);
-			Assert.Equal(app.Services, MauiApp.Current.Services);
-		}
-
-		[Fact]
-		public void HandlerContextNullBeforeBuild()
-		{
-			var app = new AppStub();
-			app.CreateBuilder();
-
-			var handlerContext = MauiApp.Current.Context;
-
-			Assert.Null(handlerContext);
-		}
-
-		[Fact]
-		public void HandlerContextAfterBuild()
-		{
-			var app = new AppStub();
-			app.CreateBuilder().Build(app);
-
-			var handlerContext = MauiApp.Current.Context;
-
-			Assert.NotNull(handlerContext);
-		}
-
-		[Fact]
-		public void CanHandlerProviderContext()
-		{
-			var app = new AppStub();
-			app.CreateBuilder().Build(app);
-
-			var handlerContext = MauiApp.Current.Context;
-
-			Assert.IsAssignableFrom<IMauiHandlersServiceProvider>(handlerContext.Handlers);
-		}
-
-		[Fact]
-		public void CanRegisterAndGetHandler()
-		{
-			var app = new AppStub();
-			app.CreateBuilder()
-				.RegisterHandler<IViewStub, ViewHandlerStub>()
-				.Build(app);
-
-			var handler = MauiApp.Current.Context.Handlers.GetHandler(typeof(IViewStub));
-			Assert.NotNull(handler);
-			Assert.IsType<ViewHandlerStub>(handler);
-		}
-
-		[Fact]
-		public void CanRegisterAndGetHandlerWithDictionary()
-		{
-			var app = new AppStub();
-			app.CreateBuilder()
-				.RegisterHandlers(new Dictionary<Type, Type>
-				{
-					{ typeof(IViewStub), typeof(ViewHandlerStub) }
-				})
-				.Build(app);
-
-			var handler = MauiApp.Current.Context.Handlers.GetHandler(typeof(IViewStub));
-			Assert.NotNull(handler);
-			Assert.IsType<ViewHandlerStub>(handler);
-		}
-
-		[Fact]
-		public void CanRegisterAndGetHandlerForType()
-		{
-			var app = new AppStub();
-			app.CreateBuilder()
-				.RegisterHandler<IViewStub, ViewHandlerStub>()
-				.Build(app);
-
-			var handler = MauiApp.Current.Context.Handlers.GetHandler(typeof(ViewStub));
-			Assert.NotNull(handler);
-			Assert.IsType<ViewHandlerStub>(handler);
-		}
-
-		[Fact]
-		public void DefaultHandlersAreRegistered()
-		{
-			var app = new AppStub();
-			app.CreateBuilder().Build(app);
-
-			var handler = MauiApp.Current.Context.Handlers.GetHandler(typeof(IButton));
-			Assert.NotNull(handler);
-			Assert.IsType<ButtonHandler>(handler);
-		}
-
-		[Fact]
-		public void CanSpecifyHandler()
-		{
-			var app = new AppStub();
-			app.CreateBuilder()
-				.RegisterHandler<ButtonStub, ButtonHandlerStub>()
-				.Build(app);
-
-			var defaultHandler = MauiApp.Current.Context.Handlers.GetHandler(typeof(IButton));
-			var specificHandler = MauiApp.Current.Context.Handlers.GetHandler(typeof(ButtonStub));
-			Assert.NotNull(defaultHandler);
-			Assert.NotNull(specificHandler);
-			Assert.IsType<ButtonHandler>(defaultHandler);
-			Assert.IsType<ButtonHandlerStub>(specificHandler);
-		}
-
-		[Fact]
-		public void WillRetrieveDifferentTransientServices()
-		{
-			var app = new AppStub();
-			app.CreateBuilder()
-				.ConfigureServices((ctx, services) => services.AddTransient<IFooService, FooService>())
-				.Build(app);
-
-			AssertTransient<IFooService, FooService>(app);
-		}
-
-		[Fact]
-		public void WillRetrieveSameSingletonServices()
-		{
-			var app = new AppStub();
-			app.CreateBuilder()
-				.ConfigureServices((ctx, services) => services.AddSingleton<IFooService, FooService>())
-				.Build(app);
-
-			AssertSingleton<IFooService, FooService>(app);
-		}
-
-		[Fact]
-		public void WillRetrieveMixedServices()
-		{
-			var app = new AppStub();
-			app.CreateBuilder()
-				.ConfigureServices((ctx, services) =>
-				{
-					services.AddSingleton<IFooService, FooService>();
-					services.AddTransient<IBarService, BarService>();
-				})
-				.Build(app);
-
-			AssertSingleton<IFooService, FooService>(app);
-			AssertTransient<IBarService, BarService>(app);
-		}
-
-		public void Dispose()
-		{
-			(App.Current as AppStub)?.ClearApp();
-		}
-
-		static void AssertTransient<TInterface, TConcrete>(AppStub app)
-		{
-			var service1 = app.Services.GetService<TInterface>();
-
-			Assert.NotNull(service1);
-			Assert.IsType<TConcrete>(service1);
-
-			var service2 = app.Services.GetService<TInterface>();
-
-			Assert.NotNull(service2);
-			Assert.IsType<TConcrete>(service2);
-
-			Assert.NotEqual(service1, service2);
-		}
-
-		static void AssertSingleton<TInterface, TConcrete>(AppStub app)
-		{
-			var service1 = app.Services.GetService<TInterface>();
-
-			Assert.NotNull(service1);
-			Assert.IsType<TConcrete>(service1);
-
-			var service2 = app.Services.GetService<TInterface>();
-
-			Assert.NotNull(service2);
-			Assert.IsType<TConcrete>(service2);
-
-			Assert.Equal(service1, service2);
-		}
-	}
-}

src/Core/tests/UnitTests/TestClasses/AppStub.cs

@@ -1,32 +1,6 @@
-using System.Collections.Generic;
-using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.Hosting;
-using Microsoft.Maui.Hosting;
-using Microsoft.Maui.UnitTests.TestClasses;
-
 namespace Microsoft.Maui.Tests
 {
-	class AppStub : MauiApp
+	class AppStub : App
 	{
-		public void ConfigureServices(HostBuilderContext ctx, IServiceCollection services)
-		{
-			services.AddSingleton<IMauiContext>(provider => new HandlersContextStub(provider));
-			services.AddTransient<IButton, ButtonStub>();
-		}
-
-		public override IAppHostBuilder CreateBuilder()
-		{
-			return base.CreateBuilder().ConfigureServices(ConfigureServices);
-		}
-
-		public override IWindow CreateWindow(IActivationState state)
-		{
-			return new WindowStub();
-		}
-
-		internal void ClearApp()
-		{
-			Current = null;
-		}
 	}
-}
+}

src/Core/tests/UnitTests/TestClasses/TestServices.cs

@@ -8,6 +8,10 @@
 	{
 	}
 
+	interface IFooBarService
+	{
+	}
+
 	class FooService : IFooService
 	{
 	}
@@ -15,4 +19,54 @@
 	class BarService : IBarService
 	{
 	}
-}
+
+	class FooBarService : IFooBarService
+	{
+		public FooBarService(IFooService foo, IBarService bar)
+		{
+			Foo = foo;
+			Bar = bar;
+		}
+
+		public IFooService Foo { get; }
+
+		public IBarService Bar { get; }
+	}
+
+	class FooDualConstructor : IFooBarService
+	{
+		public FooDualConstructor(IFooService foo)
+		{
+			Foo = foo;
+		}
+
+		public FooDualConstructor(IBarService bar)
+		{
+			Bar = bar;
+		}
+
+		public IFooService Foo { get; }
+
+		public IBarService Bar { get; }
+	}
+
+	class FooDefaultValueConstructor : IFooBarService
+	{
+		public FooDefaultValueConstructor(IBarService bar = null)
+		{
+			Bar = bar;
+		}
+
+		public IBarService Bar { get; }
+	}
+
+	class FooDefaultSystemValueConstructor : IFooBarService
+	{
+		public FooDefaultSystemValueConstructor(string text = "Default Value")
+		{
+			Text = text;
+		}
+
+		public string Text { get; }
+	}
+}

src/Core/tests/UnitTests/TestClasses/ViewHandlerStub.cs

@@ -13,7 +13,7 @@ namespace Microsoft.Maui.Tests
 
 		}
 
-		public ViewHandlerStub(PropertyMapper mapper) : base(mapper ?? MockViewMapper)
+		public ViewHandlerStub(PropertyMapper mapper = null) : base(mapper ?? MockViewMapper)
 		{
 
 		}

src/Core/tests/UnitTests/TestClasses/WindowStub.cs

@@ -1,12 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
-
-namespace Microsoft.Maui.UnitTests.TestClasses
-{
-	class WindowStub : IWindow
-	{
-		public IPage Page { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
-		public IMauiContext MauiContext { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
-	}
-}