Handle the case when response started.

Author: ilonatommy

src/Components/Endpoints/src/Rendering/EndpointHtmlRenderer.EventDispatch.cs

@@ -3,6 +3,7 @@
 
 using Microsoft.AspNetCore.Components.Rendering;
 using Microsoft.AspNetCore.Components.RenderTree;
+using Microsoft.AspNetCore.Components.Routing;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
@@ -84,6 +85,26 @@ private void SetNotFoundResponse(object? sender, EventArgs args)
         SignalRendererToFinishRendering();
     }
 
+    private void OnNavigateTo(object? sender, LocationChangedEventArgs args)
+    {
+        if (_httpContext.Response.HasStarted)
+        {
+            // We cannot redirect after the response has already started
+            RenderMetaRefreshTag(args.Location);
+        }
+        else
+        {
+            _httpContext.Response.Redirect(args.Location);
+        }
+        SignalRendererToFinishRendering();
+    }
+
+    private void RenderMetaRefreshTag(string location)
+    {
+        var metaTag = $"<meta http-equiv=\"refresh\" content=\"0;url={location}\" />";
+        _httpContext.Response.WriteAsync(metaTag);
+    }
+
     private void UpdateNamedSubmitEvents(in RenderBatch renderBatch)
     {
         if (renderBatch.NamedEventChanges is { } changes)

src/Components/Endpoints/src/Rendering/EndpointHtmlRenderer.cs

@@ -136,11 +136,6 @@ internal async Task InitializeStandardComponentServicesAsync(
         }
     }
 
-    private void OnNavigateTo(object? sender, LocationChangedEventArgs args)
-    {
-        _httpContext.Response.Redirect(args.Location);
-    }
-
     private static void InitializeResourceCollection(HttpContext httpContext)
     {
 

src/Components/test/E2ETest/ServerRenderingTests/NoInteractivityTest.cs

@@ -66,12 +66,14 @@ public void CanUseServerAuthenticationStateByDefault()
     }
 
     [Theory]
-    [InlineData(true)]
-    [InlineData(false)]
-    public void NavigatesWithoutInteractivityByRequestRedirection(bool controlFlowByException)
+    [InlineData(true, true)]
+    [InlineData(true, false)]
+    [InlineData(false, true)]
+    public void NavigatesWithoutInteractivityByRequestRedirection(bool controlFlowByException, bool isStreaming)
     {
         AppContext.SetSwitch("Microsoft.AspNetCore.Components.Endpoints.EnableThrowNavigationException", isEnabled: controlFlowByException);
-        Navigate($"{ServerPathBase}/routing/ssr-navigate-to");
+        string streaming = isStreaming ? $"streaming-" : "";
+        Navigate($"{ServerPathBase}/routing/ssr-{streaming}navigate-to");
         Browser.Equal("Click submit to navigate to home", () => Browser.Exists(By.Id("test-info")).Text);
         Browser.Click(By.Id("redirectButton"));
         Browser.Equal("Routing test cases", () => Browser.Exists(By.Id("test-info")).Text);

src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/Routing/SSRRedirectionStreaming.razor

@@ -0,0 +1,19 @@
+@page "/routing/ssr-streaming-navigate-to"
+@attribute [StreamRendering]
+@using Microsoft.AspNetCore.Components.Forms
+@inject NavigationManager NavigationManager
+
+<p id="test-info">Click submit to navigate to home</p>
+<form method="post" @onsubmit="Submit" @formname="MyUniqueFormName">
+    <AntiforgeryToken />
+    <button type="submit" id="redirectButton" class="btn btn-primary">Redirect</button>
+</form>
+
+@code {
+    private async Task Submit()
+    {
+        await Task.Delay(1000); // Simulate some async work to let the streaming begin
+        NavigationManager.NavigateTo("/subdir/routing");
+    }
+}
+