Add Results.Extensions extension helpers for returning the RazorComponentResult.

Author: SteveSandersonMS

src/Mvc/Mvc.ViewFeatures/src/Microsoft.AspNetCore.Mvc.ViewFeatures.csproj

@@ -25,6 +25,7 @@
     <Reference Include="Microsoft.AspNetCore.Antiforgery" />
     <Reference Include="Microsoft.AspNetCore.Diagnostics.Abstractions" />
     <Reference Include="Microsoft.AspNetCore.Html.Abstractions" />
+    <Reference Include="Microsoft.AspNetCore.Http.Results" />
     <Reference Include="Microsoft.Extensions.WebEncoders" />
     <Reference Include="Microsoft.AspNetCore.Components.Authorization" />
     <Reference Include="Microsoft.AspNetCore.Components.Web" />

src/Mvc/Mvc.ViewFeatures/src/PublicAPI.Unshipped.txt

@@ -5,6 +5,7 @@ Microsoft.AspNetCore.Mvc.Diagnostics.BeforeRazorComponentEventData
 Microsoft.AspNetCore.Mvc.Diagnostics.BeforeRazorComponentEventData.RenderMode.get -> Microsoft.AspNetCore.Mvc.Rendering.RenderMode
 Microsoft.AspNetCore.Mvc.Rendering.FormMethod.Dialog = 2 -> Microsoft.AspNetCore.Mvc.Rendering.FormMethod
 Microsoft.AspNetCore.Mvc.ViewFeatures.RazorComponentResult
+Microsoft.AspNetCore.Mvc.ViewFeatures.RazorComponentResultExtensions
 ~Microsoft.AspNetCore.Mvc.ViewFeatures.RazorComponentResult.Parameters.get -> object
 ~Microsoft.AspNetCore.Mvc.ViewFeatures.RazorComponentResult.Parameters.set -> void
 Microsoft.AspNetCore.Mvc.ViewFeatures.RazorComponentResult.RenderMode.get -> Microsoft.AspNetCore.Mvc.Rendering.RenderMode
@@ -29,6 +30,9 @@ Microsoft.Extensions.DependencyInjection.RazorComponentsServiceCollectionExtensi
 ~Microsoft.AspNetCore.Mvc.ViewFeatures.RazorComponentResultExecutor.RazorComponentResultExecutor(Microsoft.AspNetCore.Mvc.Infrastructure.IHttpResponseStreamWriterFactory writerFactory, System.Diagnostics.DiagnosticListener diagnosticListener) -> void
 ~Microsoft.AspNetCore.Mvc.ViewFeatures.RazorComponentResultExecutor.WriterFactory.get -> Microsoft.AspNetCore.Mvc.Infrastructure.IHttpResponseStreamWriterFactory
 ~override Microsoft.AspNetCore.Mvc.ViewFeatures.RazorComponentResult.ExecuteResultAsync(Microsoft.AspNetCore.Mvc.ActionContext context) -> System.Threading.Tasks.Task
+~static Microsoft.AspNetCore.Mvc.ViewFeatures.RazorComponentResultExtensions.RazorComponent<TComponent>(this Microsoft.AspNetCore.Http.IResultExtensions resultExtensions) -> Microsoft.AspNetCore.Mvc.IActionResult
+~static Microsoft.AspNetCore.Mvc.ViewFeatures.RazorComponentResultExtensions.RazorComponent<TComponent>(this Microsoft.AspNetCore.Http.IResultExtensions resultExtensions, Microsoft.AspNetCore.Mvc.Rendering.RenderMode renderMode, object componentParameters) -> Microsoft.AspNetCore.Mvc.IActionResult
+~static Microsoft.AspNetCore.Mvc.ViewFeatures.RazorComponentResultExtensions.RazorComponent<TComponent>(this Microsoft.AspNetCore.Http.IResultExtensions resultExtensions, object componentParameters) -> Microsoft.AspNetCore.Mvc.IActionResult
 ~static Microsoft.Extensions.DependencyInjection.RazorComponentsServiceCollectionExtensions.AddRazorComponents(this Microsoft.Extensions.DependencyInjection.IServiceCollection services) -> void
 ~static readonly Microsoft.AspNetCore.Mvc.ViewFeatures.RazorComponentResultExecutor.DefaultContentType -> string
 ~virtual Microsoft.AspNetCore.Mvc.ViewFeatures.RazorComponentResultExecutor.ExecuteAsync(Microsoft.AspNetCore.Mvc.ActionContext actionContext, Microsoft.AspNetCore.Mvc.ViewFeatures.RazorComponentResult result) -> System.Threading.Tasks.Task

src/Mvc/Mvc.ViewFeatures/src/RazorComponents/RazorComponentResultExecutor.cs

@@ -7,6 +7,7 @@
 using Microsoft.AspNetCore.Internal;
 using Microsoft.AspNetCore.Mvc.Formatters;
 using Microsoft.AspNetCore.Mvc.Infrastructure;
+using Microsoft.AspNetCore.Mvc.Rendering;
 using Microsoft.Extensions.DependencyInjection;
 
 namespace Microsoft.AspNetCore.Mvc.ViewFeatures;
@@ -93,10 +94,13 @@ private static Task RenderComponentToResponse(ActionContext actionContext, Razor
                 { nameof(RazorComponentResultHost.RazorComponentResult), result },
             });
 
+            // Note that we always use Static rendering mode for the top-level output from a RazorComponentResult,
+            // because you never want to serialize the invocation of RazorComponentResultHost. Instead, that host
+            // component takes care of switching into your desired render mode when it produces its own output.
             var htmlContent = await componentPrerenderer.PrerenderComponentAsync(
                 actionContext,
                 typeof(RazorComponentResultHost),
-                result.RenderMode,
+                RenderMode.Static,
                 hostParameters);
             await htmlContent.WriteToAsync(writer);
         });

src/Mvc/Mvc.ViewFeatures/src/RazorComponents/RazorComponentResultExtensions.cs

@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Microsoft.AspNetCore.Components;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc.Rendering;
+
+namespace Microsoft.AspNetCore.Mvc.ViewFeatures;
+
+/// <summary>
+/// Holds extension methods on <see cref="IResultExtensions"/>.
+/// </summary>
+public static class RazorComponentResultExtensions
+{
+    /// <summary>
+    /// Returns an <see cref="IActionResult"/> that renders a Razor Component.
+    /// </summary>
+    /// <typeparam name="TComponent">The type of component to render.</typeparam>
+    /// <param name="resultExtensions">The <see cref="ResultExtensions"/>.</param>
+    /// <returns>An <see cref="IActionResult"/> that renders a Razor Component.</returns>
+    public static IActionResult RazorComponent<TComponent>(this IResultExtensions resultExtensions) where TComponent : IComponent
+        => new RazorComponentResult(typeof(TComponent));
+
+    /// <summary>
+    /// Returns an <see cref="IActionResult"/> that renders a Razor Component.
+    /// </summary>
+    /// <typeparam name="TComponent">The type of component to render.</typeparam>
+    /// <param name="resultExtensions">The <see cref="ResultExtensions"/>.</param>
+    /// <param name="componentParameters">Parameters for the component.</param>
+    /// <returns>An <see cref="IActionResult"/> that renders a Razor Component.</returns>
+    public static IActionResult RazorComponent<TComponent>(this IResultExtensions resultExtensions, object componentParameters) where TComponent : IComponent
+        => new RazorComponentResult(typeof(TComponent)) { Parameters = componentParameters };
+
+    /// <summary>
+    /// Returns an <see cref="IActionResult"/> that renders a Razor Component.
+    /// </summary>
+    /// <typeparam name="TComponent">The type of component to render.</typeparam>
+    /// <param name="resultExtensions">The <see cref="ResultExtensions"/>.</param>
+    /// <param name="componentParameters">Parameters for the component.</param>
+    /// <param name="renderMode">A <see cref="RenderMode"/> value that specifies how to render the component.</param>
+    /// <returns>An <see cref="IActionResult"/> that renders a Razor Component.</returns>
+    public static IActionResult RazorComponent<TComponent>(this IResultExtensions resultExtensions, RenderMode renderMode, object componentParameters) where TComponent: IComponent
+        => new RazorComponentResult(typeof(TComponent)) { RenderMode = renderMode, Parameters = componentParameters };
+}

src/Mvc/Mvc.ViewFeatures/src/RazorComponents/RazorComponentResultHost.cs

@@ -61,9 +61,15 @@ private void BuildRenderTree(RenderTreeBuilder builder)
 
     private void RenderPageWithParameters(RenderTreeBuilder builder)
     {
-        // If we wanted to support rendering pre-instantiated component objects, it would probably go here
-        // as either a whole new RenderTreeFrame type or as some mechanism to attach the instance onto a
-        // regular Component frame (perhaps using a dummy ComponentState that represents 'not yet initialized')
+        // TODO: Once we support rendering Server/WebAssembly components into the page, implementation will
+        // go here. We need to switch into the rendermode given by RazorComponentResult.RenderMode for this
+        // child component. That will cause the developer-supplied parameters to be serialized into a marker
+        // but not attempt to serialize the RenderFragment that causes this to be hosted in its layout.
+
+        // TODO: If we wanted to support rendering pre-instantiated component objects, it would probably go here
+        // as either a whole new RenderTreeFrame type or as some mechanism to attach the instance onto a regular
+        // Component frame (perhaps using a dummy ComponentState that represents 'not yet initialized')
+
         builder.OpenComponent(0, RazorComponentResult.ComponentType);
 
         if (RazorComponentResult.Parameters is not null)