fix: Add WithMessageBus and TaskPool schedulers with RxAppBuilder

src/ReactiveUI.AndroidX/Builder/AndroidXReactiveUIBuilderExtensions.cs

@@ -34,6 +34,7 @@ public static IReactiveUIBuilder WithAndroidX(this IReactiveUIBuilder builder)
 
         return builder
             .WithMainThreadScheduler(HandlerScheduler.MainThreadScheduler)
+            .WithTaskPoolScheduler(TaskPoolScheduler.Default)
             .WithPlatformModule<AndroidX.Registrations>();
     }
 

src/ReactiveUI.Blazor/Builder/BlazorReactiveUIBuilderExtensions.cs

@@ -40,6 +40,25 @@ public static IReactiveUIBuilder WithBlazor(this IReactiveUIBuilder builder)
 
         return builder
             .WithBlazorScheduler()
+            .WithTaskPoolScheduler(TaskPoolScheduler.Default)
+            .WithPlatformModule<Blazor.Registrations>();
+    }
+
+    /// <summary>
+    /// Configures ReactiveUI for Blazor platform with appropriate schedulers.
+    /// </summary>
+    /// <param name="builder">The builder instance.</param>
+    /// <returns>The builder instance for chaining.</returns>
+    public static IReactiveUIBuilder WithBlazorWasm(this IReactiveUIBuilder builder)
+    {
+        if (builder is null)
+        {
+            throw new ArgumentNullException(nameof(builder));
+        }
+
+        return builder
+            .WithBlazorWasmScheduler()
+            .WithTaskPoolScheduler(TaskPoolScheduler.Default)
             .WithPlatformModule<Blazor.Registrations>();
     }
 

src/ReactiveUI.Blazor/Registrations.cs

@@ -46,8 +46,5 @@ public void Register(IRegistrar registrar)
         {
             PlatformEnlightenmentProvider.Current.EnableWasm();
         }
-
-        RxSchedulers.TaskpoolScheduler = TaskPoolScheduler.Default;
-        RxSchedulers.MainThreadScheduler = CurrentThreadScheduler.Instance;
     }
 }

src/ReactiveUI.Maui/Builder/MauiReactiveUIBuilderExtensions.cs

@@ -70,6 +70,7 @@ public static IReactiveUIBuilder WithMaui(this IReactiveUIBuilder builder, IDisp
 
         return builder
             .WithMauiScheduler(dispatcher)
+            .WithTaskPoolScheduler(TaskPoolScheduler.Default)
             .WithPlatformModule<Maui.Registrations>()
             .WithPlatformServices();
     }

src/ReactiveUI.Maui/Registrations.cs

@@ -36,12 +36,6 @@ public void Register(IRegistrar registrar)
         registrar.RegisterConstant<IPropertyBindingHook>(static () => new AutoDataTemplateBindingHook());
         registrar.RegisterConstant<IBindingFallbackConverter>(static () => new ComponentModelFallbackConverter());
 
-        if (!ModeDetector.InUnitTestRunner())
-        {
-            RxSchedulers.MainThreadScheduler = new WaitForDispatcherScheduler(static () => DispatcherQueueScheduler.Current);
-            RxSchedulers.TaskpoolScheduler = TaskPoolScheduler.Default;
-        }
-
         RxSchedulers.SuppressViewCommandBindingMessage = true;
 #endif
     }

src/ReactiveUI.WinUI/Builder/WinUIReactiveUIBuilderExtensions.cs

@@ -29,6 +29,7 @@ public static IReactiveUIBuilder WithWinUI(this IReactiveUIBuilder builder)
 
         return builder
             .WithWinUIScheduler()
+            .WithTaskPoolScheduler(TaskPoolScheduler.Default)
             .WithPlatformModule<WinUI.Registrations>();
     }
 

src/ReactiveUI.Winforms/Builder/WinFormsReactiveUIBuilderExtensions.cs

@@ -33,6 +33,7 @@ public static IReactiveUIBuilder WithWinForms(this IReactiveUIBuilder builder)
 
         return builder
             .WithMainThreadScheduler(WinFormsMainThreadScheduler)
+            .WithTaskPoolScheduler(TaskPoolScheduler.Default)
             .WithPlatformModule<Winforms.Registrations>();
     }
 

src/ReactiveUI.Winforms/Registrations.cs

@@ -31,7 +31,6 @@ public void Register(IRegistrar registrar)
         if (!ModeDetector.InUnitTestRunner())
         {
             WindowsFormsSynchronizationContext.AutoInstall = true;
-            RxSchedulers.MainThreadScheduler = new WaitForDispatcherScheduler(static () => new SynchronizationContextScheduler(new WindowsFormsSynchronizationContext()));
         }
     }
 }

src/ReactiveUI.Wpf/Builder/WpfReactiveUIBuilderExtensions.cs

@@ -32,7 +32,8 @@ public static IReactiveUIBuilder WithWpf(this IReactiveUIBuilder builder)
         return builder
             .WithPlatformModule<Wpf.Registrations>()
             .WithPlatformServices()
-            .WithWpfScheduler();
+            .WithWpfScheduler()
+            .WithTaskPoolScheduler(TaskPoolScheduler.Default);
     }
 
     /// <summary>

src/ReactiveUI.Wpf/Registrations.cs

@@ -29,13 +29,6 @@ public void Register(IRegistrar registrar)
         registrar.RegisterConstant<IPropertyBindingHook>(static () => new AutoDataTemplateBindingHook());
         registrar.RegisterConstant<IBindingFallbackConverter>(static () => new ComponentModelFallbackConverter());
 
-        if (!ModeDetector.InUnitTestRunner())
-        {
-            // NB: On .NET Core, trying to touch DispatcherScheduler blows up :cry:
-            RxSchedulers.MainThreadScheduler = new WaitForDispatcherScheduler(static () => DispatcherScheduler.Current);
-            RxSchedulers.TaskpoolScheduler = TaskPoolScheduler.Default;
-        }
-
         RxSchedulers.SuppressViewCommandBindingMessage = true;
     }
 }

src/ReactiveUI/Builder/IReactiveUIBuilder.cs

@@ -38,12 +38,18 @@ namespace ReactiveUI.Builder;
 /// <seealso cref="IAppBuilder" />
 public interface IReactiveUIBuilder : IAppBuilder
 {
+    /// <summary>
+    /// Configures the message bus.
+    /// </summary>
+    /// <returns>The builder instance for chaining.</returns>
+    IReactiveUIBuilder WithMessageBus();
+
     /// <summary>
     /// Configures the message bus.
     /// </summary>
     /// <param name="configure">A delegate to configure the message bus.</param>
     /// <returns>The builder instance for chaining.</returns>
-    IReactiveUIBuilder ConfigureMessageBus(Action<MessageBus> configure);
+    IReactiveUIBuilder WithMessageBus(Action<IMessageBus> configure);
 
     /// <summary>
     /// Registers a custom message bus instance.
@@ -121,6 +127,18 @@ IReactiveUIBuilder RegisterView<TView, TViewModel>()
     IReactiveUIBuilder RegisterViewModel<TViewModel>()
         where TViewModel : class, IReactiveObject, new();
 
+    /// <summary>
+    /// Registers a constant instance of the specified view model type for use in the reactive UI builder.
+    /// </summary>
+    /// <remarks>The registered view model instance is created once using its parameterless constructor and
+    /// reused for all requests. Use this method when the view model does not require per-request state or
+    /// dependencies.</remarks>
+    /// <typeparam name="TViewModel">The type of the view model to register. Must be a reference type that implements IReactiveObject and has a
+    /// parameterless constructor.</typeparam>
+    /// <returns>The current instance of the reactive UI builder, enabling method chaining.</returns>
+    IReactiveUIBuilder RegisterConstantViewModel<TViewModel>()
+        where TViewModel : class, IReactiveObject, new();
+
     /// <summary>
     /// Withes the main thread scheduler.
     /// </summary>

src/ReactiveUI/Builder/ReactiveUIBuilder.cs

@@ -272,19 +272,29 @@ public IReactiveUIBuilder ForPlatforms(params Action<IReactiveUIBuilder>[] platf
         return this;
     }
 
+    /// <summary>
+    /// Configures the ReactiveUI message bus.
+    /// </summary>
+    /// <returns>The builder instance for chaining.</returns>
+    public IReactiveUIBuilder WithMessageBus() =>
+        WithRegistrationOnBuild(resolver =>
+        {
+            _messageBus = new MessageBus();
+            resolver.RegisterConstant<IMessageBus>(_messageBus);
+        });
+
     /// <summary>
     /// Configures the ReactiveUI message bus.
     /// </summary>
     /// <param name="configure">The configuration action.</param>
     /// <returns>The builder instance for chaining.</returns>
-    public IReactiveUIBuilder ConfigureMessageBus(Action<MessageBus> configure) =>
+    public IReactiveUIBuilder WithMessageBus(Action<IMessageBus> configure) =>
         WithRegistrationOnBuild(resolver =>
-            resolver.Register<IMessageBus>(() =>
-            {
-                var messageBus = new MessageBus();
-                configure(messageBus);
-                return messageBus;
-            }));
+        {
+            _messageBus = new MessageBus();
+            configure(_messageBus);
+            resolver.RegisterConstant<IMessageBus>(_messageBus);
+        });
 
     /// <summary>
     /// Registers a custom message bus instance.
@@ -632,6 +642,18 @@ public IReactiveUIBuilder RegisterViewModel<TViewModel>()
         where TViewModel : class, IReactiveObject, new() =>
             WithRegistration(static resolver => resolver.Register<TViewModel>(static () => new()));
 
+    /// <summary>
+    /// Registers a constant instance of the specified view model type in the dependency resolver.
+    /// </summary>
+    /// <remarks>This method creates a single instance of the specified view model type and registers it as a
+    /// constant in the resolver. All requests for this view model type will return the same instance.</remarks>
+    /// <typeparam name="TViewModel">The type of the view model to register. Must be a class that implements IReactiveObject and has a parameterless
+    /// constructor.</typeparam>
+    /// <returns>The current builder instance, enabling further configuration of the dependency resolver.</returns>
+    public IReactiveUIBuilder RegisterConstantViewModel<TViewModel>()
+        where TViewModel : class, IReactiveObject, new() =>
+            WithRegistration(static resolver => resolver.RegisterConstant(new TViewModel()));
+
     /// <summary>
     /// Registers a custom view model with the dependency resolver.
     /// </summary>

src/ReactiveUI/Mixins/BuilderMixins.cs

@@ -306,6 +306,22 @@ public static IReactiveUIBuilder ForPlatforms(this IReactiveUIBuilder reactiveUI
         return reactiveUIBuilder;
     }
 
+    /// <summary>
+    /// Configures the ReactiveUI message bus.
+    /// </summary>
+    /// <param name="reactiveUIBuilder">The reactive UI builder.</param>
+    /// <returns>
+    /// The builder instance for chaining.
+    /// </returns>
+    /// <exception cref="ArgumentNullException">reactiveUIBuilder.</exception>
+    public static IReactiveUIBuilder WithMessageBus(this IReactiveUIBuilder reactiveUIBuilder)
+    {
+        ArgumentExceptionHelper.ThrowIfNull(reactiveUIBuilder);
+
+        reactiveUIBuilder.WithMessageBus();
+        return reactiveUIBuilder;
+    }
+
     /// <summary>
     /// Configures the ReactiveUI message bus.
     /// </summary>
@@ -315,11 +331,11 @@ public static IReactiveUIBuilder ForPlatforms(this IReactiveUIBuilder reactiveUI
     /// The builder instance for chaining.
     /// </returns>
     /// <exception cref="ArgumentNullException">reactiveUIBuilder.</exception>
-    public static IReactiveUIBuilder ConfigureMessageBus(this IReactiveUIBuilder reactiveUIBuilder, Action<MessageBus> configure)
+    public static IReactiveUIBuilder WithMessageBus(this IReactiveUIBuilder reactiveUIBuilder, Action<IMessageBus> configure)
     {
         ArgumentExceptionHelper.ThrowIfNull(reactiveUIBuilder);
 
-        reactiveUIBuilder.ConfigureMessageBus(configure);
+        reactiveUIBuilder.WithMessageBus(configure);
         return reactiveUIBuilder;
     }
 
@@ -392,6 +408,22 @@ public static IReactiveUIBuilder RegisterViewModel<TViewModel>(this IReactiveUIB
         return reactiveUIBuilder;
     }
 
+    /// <summary>
+    /// Registers a constant instance of the specified view model type for use with the ReactiveUI builder.
+    /// </summary>
+    /// <typeparam name="TViewModel">The type of the view model to register. Must be a class that implements IReactiveObject and has a parameterless
+    /// constructor.</typeparam>
+    /// <param name="reactiveUIBuilder">The ReactiveUI builder to configure. Cannot be null.</param>
+    /// <returns>The same ReactiveUI builder instance, to allow for method chaining.</returns>
+    public static IReactiveUIBuilder RegisterConstantViewModel<TViewModel>(this IReactiveUIBuilder reactiveUIBuilder)
+        where TViewModel : class, IReactiveObject, new()
+    {
+        ArgumentExceptionHelper.ThrowIfNull(reactiveUIBuilder);
+
+        reactiveUIBuilder.RegisterConstantViewModel<TViewModel>();
+        return reactiveUIBuilder;
+    }
+
     /// <summary>
     /// Registers a custom view model with the dependency resolver.
     /// </summary>

src/examples/ReactiveUI.Builder.BlazorServer/Program.cs

@@ -8,8 +8,6 @@
 using ReactiveUI.Builder.BlazorServer.Components;
 using ReactiveUI.Builder.BlazorServer.Services;
 using ReactiveUI.Builder.BlazorServer.ViewModels;
-using ReactiveUI.Builder.BlazorServer.Views;
-using Splat;
 using Splat.Microsoft.Extensions.DependencyInjection;
 
 var builder = WebApplication.CreateBuilder(args);
@@ -30,14 +28,8 @@
 
 RxAppBuilder.CreateReactiveUIBuilder()
    .WithBlazor()
+   .WithMessageBus()
    .WithViewsFromAssembly(typeof(Program).Assembly)
-   .WithRegistration(locator =>
-   {
-       if (Locator.Current.GetService<IMessageBus>() is null)
-       {
-           locator.RegisterConstant(MessageBus.Current);
-       }
-   })
    .BuildApp();
 
 var app = builder.Build();

src/examples/ReactiveUI.Builder.BlazorServer/ReactiveUI.Builder.BlazorServer.csproj

@@ -4,6 +4,7 @@
     <TargetFramework>net10.0</TargetFramework>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
+    <IsPackable>false</IsPackable>
     <BlazorDisableThrowNavigationException>true</BlazorDisableThrowNavigationException>
     <DefaultPackageDescription>Blazor Server example app for ReactiveUI Builder.</DefaultPackageDescription>
   </PropertyGroup>

src/examples/ReactiveUI.Builder.BlazorServer/Services/FileJsonSuspensionDriver.cs

@@ -3,7 +3,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for full license information.
 
-using System.IO;
 using System.Reactive;
 using System.Reactive.Linq;
 using System.Text.Json;
@@ -70,7 +69,7 @@ public IObservable<Unit> InvalidateState() => Observable.Start(
     {
         if (!File.Exists(path))
         {
-            return default(T);
+            return default;
         }
 
         var json = File.ReadAllText(path);

src/examples/ReactiveUI.Builder.BlazorServer/Services/ReactiveUiAppHostedService.cs

@@ -5,8 +5,6 @@
 
 using System.Diagnostics;
 using System.Reactive.Linq;
-using Microsoft.Extensions.Hosting;
-using ReactiveUI;
 using ReactiveUI.Builder.BlazorServer.Models;
 using Splat;
 

src/examples/ReactiveUI.Builder.BlazorServer/Views/LobbyView.razor.cs

@@ -5,7 +5,6 @@
 
 using System.Reactive.Linq;
 using Microsoft.AspNetCore.Components.Web;
-using ReactiveUI;
 using ReactiveUI.Blazor;
 using ReactiveUI.Builder.BlazorServer.Models;
 using ReactiveUI.Builder.BlazorServer.ViewModels;

src/examples/ReactiveUI.Builder.WpfApp/App.xaml.cs

@@ -35,7 +35,7 @@ protected override void OnStartup(StartupEventArgs e)
         base.OnStartup(e);
 
         // Initialize ReactiveUI via the Builder only
-        RxAppBuilder.CreateReactiveUIBuilder()
+        var app = RxAppBuilder.CreateReactiveUIBuilder()
             .WithWpf()
             .WithViewsFromAssembly(typeof(App).Assembly) // auto-register all IViewFor in this assembly
                                                          ////.RegisterView<MainWindow, ViewModels.AppBootstrapper>()
@@ -52,17 +52,12 @@ protected override void OnStartup(StartupEventArgs e)
                     Debugger.Break();
                 }
             }))
+            .WithMessageBus()
             .WithRegistration(static r =>
             {
                 // Register IScreen as a singleton so all resolutions share the same Router
                 r.RegisterLazySingleton<IScreen>(static () => new ViewModels.AppBootstrapper());
 
-                // Register MessageBus as a singleton if not already
-                if (Locator.Current.GetService<IMessageBus>() is null)
-                {
-                    r.RegisterConstant(MessageBus.Current);
-                }
-
                 // Cross-process instance lifetime coordination
                 r.RegisterLazySingleton(static () => new Services.AppLifetimeCoordinator());
 

src/examples/ReactiveUI.Builder.WpfApp/Models/RoomEventMessage.cs

@@ -3,7 +3,9 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for full license information.
 
-namespace ReactiveUI.Builder.WpfApp.Services;
+using ReactiveUI.Builder.WpfApp.Services;
+
+namespace ReactiveUI.Builder.WpfApp.Models;
 
 /// <summary>
 /// Network event describing a change in the rooms list.

src/examples/ReactiveUI.Builder.WpfApp/ReactiveUI.Builder.WpfApp.csproj

@@ -19,6 +19,14 @@
 
   <ItemGroup>
     <Using Include="ReactiveUI.Helpers" />
+    <Using Include="System.Collections.ObjectModel" />
+    <Using Include="System.IO.MemoryMappedFiles" />
+    <Using Include="System.Diagnostics" />
+    <Using Include="System.Net" />
+    <Using Include="System.Net.Sockets" />
+    <Using Include="System.Reactive" />
+    <Using Include="System.Reactive.Linq" />
+    <Using Include="System.Text.Json" />
   </ItemGroup>
 
 </Project>