From 5fff491735d23faab0f3c14f58f6e10d7119fbcb Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Wed, 21 May 2025 13:25:26 +0200
Subject: [PATCH 01/20] Add re-exec tests for SSR + move NotFound sources into
 one directory.

---
 .../NoInteractivityTest.cs                    | 28 ++++++++++++++++
 ...omponentEndpointsNoInteractivityStartup.cs | 33 ++++++++++++-------
 .../RazorComponentEndpointsStartup.cs         |  2 +-
 .../Pages/{ => NotFound}/NotFoundPage.razor   |  0
 .../{ => NotFound}/PageThatSetsNotFound.razor |  0
 .../Pages/NotFound/RedirectionNotFound.razor  | 28 ++++++++++++++++
 .../Pages/{ => NotFound}/ReexecutedPage.razor |  0
 7 files changed, 79 insertions(+), 12 deletions(-)
 rename src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/{ => NotFound}/NotFoundPage.razor (100%)
 rename src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/{ => NotFound}/PageThatSetsNotFound.razor (100%)
 create mode 100644 src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound.razor
 rename src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/{ => NotFound}/ReexecutedPage.razor (100%)

diff --git a/src/Components/test/E2ETest/ServerRenderingTests/NoInteractivityTest.cs b/src/Components/test/E2ETest/ServerRenderingTests/NoInteractivityTest.cs
index 139f3db4726e..e54125e46937 100644
--- a/src/Components/test/E2ETest/ServerRenderingTests/NoInteractivityTest.cs
+++ b/src/Components/test/E2ETest/ServerRenderingTests/NoInteractivityTest.cs
@@ -87,6 +87,34 @@ public void CanRenderNotFoundPageAfterStreamingStarted()
         Browser.Equal("Default Not Found Page", () => Browser.Title);
     }
 
+    [Fact]
+    public void ProgrammaticNavigationToNotExistingPathReExecutesTo404()
+    {
+        Navigate($"{ServerPathBase}/reexecution/redirection-not-found?navigate-programmatically=true");
+        Assert404ReExecuted();
+    }
+
+    [Fact]
+    public void LinkNavigationToNotExistingPathReExecutesTo404()
+    {
+        Navigate($"{ServerPathBase}/reexecution/redirection-not-found");
+        Browser.Click(By.Id("link-to-not-existing-page"));
+        Assert404ReExecuted();
+    }
+
+    [Fact]
+    public void BrowserNavigationToNotExistingPathReExecutesTo404()
+    {
+        // non-existing path has to have re-execution middleware set up
+        // so it has to have "reexecution" prefix. Otherwise middleware mapping
+        // will not be activated, see configuration in Startup
+        Navigate($"{ServerPathBase}/reexecution/not-existing-page");
+        Assert404ReExecuted();
+    }
+
+    private void Assert404ReExecuted() =>
+        Browser.Equal("Welcome On Page Re-executed After Not Found Event", () => Browser.Exists(By.Id("test-info")).Text);
+
     [Theory]
     [InlineData(true)]
     [InlineData(false)]
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs
index c4af233c40fe..d072d9b444b0 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs
@@ -48,19 +48,30 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
 
         app.Map("/subdir", app =>
         {
-            if (!env.IsDevelopment())
+            app.Map("/reexecution", reexecutionApp =>
             {
-                app.UseExceptionHandler("/Error", createScopeForErrors: true);
-            }
-
-            app.UseStaticFiles();
-            app.UseRouting();
-            RazorComponentEndpointsStartup<TRootComponent>.UseFakeAuthState(app);
-            app.UseAntiforgery();
-            app.UseEndpoints(endpoints =>
-            {
-                endpoints.MapRazorComponents<TRootComponent>();
+                reexecutionApp.UseStatusCodePagesWithReExecute("/not-found-reexecute", createScopeForErrors: true);
+                ConfigureSubdirPipeline(reexecutionApp, env);
             });
+
+            ConfigureSubdirPipeline(app, env);
+        });
+    }
+
+    private void ConfigureSubdirPipeline(IApplicationBuilder app, IWebHostEnvironment env)
+    {
+        if (!env.IsDevelopment())
+        {
+            app.UseExceptionHandler("/Error", createScopeForErrors: true);
+        }
+
+        app.UseStaticFiles();
+        app.UseRouting();
+        RazorComponentEndpointsStartup<TRootComponent>.UseFakeAuthState(app);
+        app.UseAntiforgery();
+        app.UseEndpoints(endpoints =>
+        {
+            endpoints.MapRazorComponents<TRootComponent>();
         });
     }
 }
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
index f91db9aa4ee3..9aa6f62b2bb1 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
@@ -89,7 +89,7 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
         });
     }
 
-    protected virtual void ConfigureSubdirPipeline(IApplicationBuilder app, IWebHostEnvironment env)
+    private void ConfigureSubdirPipeline(IApplicationBuilder app, IWebHostEnvironment env)
     {
         WebAssemblyTestHelper.ServeCoopHeadersIfWebAssemblyThreadingEnabled(app);
 
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFoundPage.razor b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/NotFoundPage.razor
similarity index 100%
rename from src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFoundPage.razor
rename to src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/NotFoundPage.razor
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/PageThatSetsNotFound.razor b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/PageThatSetsNotFound.razor
similarity index 100%
rename from src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/PageThatSetsNotFound.razor
rename to src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/PageThatSetsNotFound.razor
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound.razor b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound.razor
new file mode 100644
index 000000000000..97a422dc90b2
--- /dev/null
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound.razor
@@ -0,0 +1,28 @@
+@page "/redirection-not-found"
+@page "/reexecution/redirection-not-found"
+@attribute [StreamRendering(false)]
+@inject NavigationManager NavigationManager
+
+<PageTitle>Original page</PageTitle>
+
+<p id="test-info">Any content</p>
+<a id="link-to-not-existing-page" href="@(_nonExistingPath)">
+    Go to not-existing-page
+</a>
+
+@code{
+    [Parameter]
+    [SupplyParameterFromQuery(Name = "navigate-programmatically")]
+    public bool? NavigateProgrammatically { get; set; }
+
+    private string? _nonExistingPath;
+
+    protected override void OnInitialized()
+    {
+        _nonExistingPath = $"{NavigationManager.BaseUri}not-existing-page";
+        if (NavigateProgrammatically == true)
+        {
+            NavigationManager.NavigateTo(_nonExistingPath);
+        }
+    }
+}
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/ReexecutedPage.razor b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/ReexecutedPage.razor
similarity index 100%
rename from src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/ReexecutedPage.razor
rename to src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/ReexecutedPage.razor

From 66cc9747693b2e3bc946cc5ab7ed051f6acff204 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Wed, 21 May 2025 13:57:04 +0200
Subject: [PATCH 02/20] Per-component interactivity: test navigation to
 non-existing page.

---
 .../ServerRenderingTests/InteractivityTest.cs | 37 +++++++++++++++++++
 .../RedirectionNotFound-Interactive.razor     | 32 ++++++++++++++++
 ...nd.razor => RedirectionNotFound-SSR.razor} |  0
 3 files changed, 69 insertions(+)
 create mode 100644 src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-Interactive.razor
 rename src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/{RedirectionNotFound.razor => RedirectionNotFound-SSR.razor} (100%)

diff --git a/src/Components/test/E2ETest/ServerRenderingTests/InteractivityTest.cs b/src/Components/test/E2ETest/ServerRenderingTests/InteractivityTest.cs
index 286a6de9e12d..5dec3281e98a 100644
--- a/src/Components/test/E2ETest/ServerRenderingTests/InteractivityTest.cs
+++ b/src/Components/test/E2ETest/ServerRenderingTests/InteractivityTest.cs
@@ -1411,4 +1411,41 @@ public void NavigatesWithInteractivityByRequestRedirection(bool controlFlowByExc
         Browser.Click(By.Id("redirectButton"));
         Browser.Equal("Routing test cases", () => Browser.Exists(By.Id("test-info")).Text);
     }
+
+    [Theory]
+    // prerendering (SSR) is tested in NoInteractivityTest
+    [InlineData("ServerNonPrerendered")]
+    [InlineData("WebAssemblyNonPrerendered")]
+    public void ProgrammaticNavigationToNotExistingPathReExecutesTo404(string renderMode)
+    {
+        Navigate($"{ServerPathBase}/reexecution/redirection-not-found?render-mode={renderMode}&navigate-programmatically=true");
+        Assert404ReExecuted();
+    }
+
+    [Theory]
+    // prerendering (SSR) is tested in NoInteractivityTest
+    [InlineData("ServerNonPrerendered")]
+    [InlineData("WebAssemblyNonPrerendered")]
+    public void LinkNavigationToNotExistingPathReExecutesTo404(string renderMode)
+    {
+        Navigate($"{ServerPathBase}/reexecution/redirection-not-found?render-mode={renderMode}");
+        Browser.Click(By.Id("link-to-not-existing-page"));
+        Assert404ReExecuted();
+    }
+
+    [Theory]
+    // prerendering (SSR) is tested in NoInteractivityTest
+    [InlineData("ServerNonPrerendered")]
+    [InlineData("WebAssemblyNonPrerendered")]
+    public void BrowserNavigationToNotExistingPathReExecutesTo404(string renderMode)
+    {
+        // non-existing path has to have re-execution middleware set up
+        // so it has to have "reexecution" prefix. Otherwise middleware mapping
+        // will not be activated, see configuration in Startup
+        Navigate($"{ServerPathBase}/reexecution/not-existing-page?render-mode={renderMode}");
+        Assert404ReExecuted();
+    }
+
+    private void Assert404ReExecuted() =>
+        Browser.Equal("Welcome On Page Re-executed After Not Found Event", () => Browser.Exists(By.Id("test-info")).Text);
 }
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-Interactive.razor b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-Interactive.razor
new file mode 100644
index 000000000000..01351b40bb8a
--- /dev/null
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-Interactive.razor
@@ -0,0 +1,32 @@
+@page "/redirection-not-found"
+@page "/reexecution/redirection-not-found"
+@rendermode @(RenderModeHelper.GetRenderMode(_currentRenderMode))
+@inject NavigationManager NavigationManager
+
+<PageTitle>Original page</PageTitle>
+
+<p id="test-info">Any content</p>
+<a id="link-to-not-existing-page" href="@(_nonExistingPath)">
+    Go to not-existing-page
+</a>
+
+@code{
+    [Parameter, SupplyParameterFromQuery(Name = "renderMode")]
+    public string? RenderModeStr { get; set; }
+
+    [Parameter]
+    [SupplyParameterFromQuery(Name = "navigate-programmatically")]
+    public bool? NavigateProgrammatically { get; set; }
+
+    private string? _nonExistingPath;
+    private RenderModeId _currentRenderMode => RenderModeHelper.ParseRenderMode(RenderModeStr);
+
+    protected override void OnInitialized()
+    {
+        _nonExistingPath = $"{NavigationManager.BaseUri}not-existing-page";
+        if (NavigateProgrammatically == true)
+        {
+            NavigationManager.NavigateTo(_nonExistingPath);
+        }
+    }
+}
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound.razor b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR.razor
similarity index 100%
rename from src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound.razor
rename to src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR.razor

From 89075246f9fbdf16eb5e90c63b748d03f21a5c07 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Wed, 21 May 2025 15:07:50 +0200
Subject: [PATCH 03/20] Add streaming SSR tests.

---
 .../NoInteractivityTest.cs                    | 27 +++++++++++------
 .../RedirectionNotFound-SSR-streaming.razor   |  5 ++++
 .../NotFound/RedirectionNotFound-SSR.razor    | 29 ++-----------------
 .../RedirectionNotFoundComponent.razor        | 26 +++++++++++++++++
 .../Pages/NotFoundSSR.razor                   | 11 -------
 5 files changed, 52 insertions(+), 46 deletions(-)
 create mode 100644 src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR-streaming.razor
 create mode 100644 src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFoundComponent.razor
 delete mode 100644 src/Components/test/testassets/Components.WasmMinimal/Pages/NotFoundSSR.razor

diff --git a/src/Components/test/E2ETest/ServerRenderingTests/NoInteractivityTest.cs b/src/Components/test/E2ETest/ServerRenderingTests/NoInteractivityTest.cs
index e54125e46937..c7af49fc7b3f 100644
--- a/src/Components/test/E2ETest/ServerRenderingTests/NoInteractivityTest.cs
+++ b/src/Components/test/E2ETest/ServerRenderingTests/NoInteractivityTest.cs
@@ -87,28 +87,37 @@ public void CanRenderNotFoundPageAfterStreamingStarted()
         Browser.Equal("Default Not Found Page", () => Browser.Title);
     }
 
-    [Fact]
-    public void ProgrammaticNavigationToNotExistingPathReExecutesTo404()
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void ProgrammaticNavigationToNotExistingPathReExecutesTo404(bool streaming)
     {
-        Navigate($"{ServerPathBase}/reexecution/redirection-not-found?navigate-programmatically=true");
+        string streamingPath = streaming ? "-streaming" : "";
+        Navigate($"{ServerPathBase}/reexecution/redirection-not-found-ssr{streamingPath}?navigate-programmatically=true");
         Assert404ReExecuted();
     }
 
-    [Fact]
-    public void LinkNavigationToNotExistingPathReExecutesTo404()
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void LinkNavigationToNotExistingPathReExecutesTo404(bool streaming)
     {
-        Navigate($"{ServerPathBase}/reexecution/redirection-not-found");
+        string streamingPath = streaming ? "-streaming" : "";
+        Navigate($"{ServerPathBase}/reexecution/redirection-not-found-ssr{streamingPath}");
         Browser.Click(By.Id("link-to-not-existing-page"));
         Assert404ReExecuted();
     }
 
-    [Fact]
-    public void BrowserNavigationToNotExistingPathReExecutesTo404()
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void BrowserNavigationToNotExistingPathReExecutesTo404(bool streaming)
     {
         // non-existing path has to have re-execution middleware set up
         // so it has to have "reexecution" prefix. Otherwise middleware mapping
         // will not be activated, see configuration in Startup
-        Navigate($"{ServerPathBase}/reexecution/not-existing-page");
+        string streamingPath = streaming ? "-streaming" : "";
+        Navigate($"{ServerPathBase}/reexecution/not-existing-page-ssr{streamingPath}");
         Assert404ReExecuted();
     }
 
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR-streaming.razor b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR-streaming.razor
new file mode 100644
index 000000000000..07781aa37637
--- /dev/null
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR-streaming.razor
@@ -0,0 +1,5 @@
+@page "/redirection-not-found-ssr-streaming"
+@page "/reexecution/redirection-not-found-ssr-streaming"
+@attribute [StreamRendering(true)]
+
+<RedirectionNotFoundComponent />
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR.razor b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR.razor
index 97a422dc90b2..d69ef0f4acbf 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR.razor
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR.razor
@@ -1,28 +1,5 @@
-@page "/redirection-not-found"
-@page "/reexecution/redirection-not-found"
+@page "/redirection-not-found-ssr"
+@page "/reexecution/redirection-not-found-ssr"
 @attribute [StreamRendering(false)]
-@inject NavigationManager NavigationManager
 
-<PageTitle>Original page</PageTitle>
-
-<p id="test-info">Any content</p>
-<a id="link-to-not-existing-page" href="@(_nonExistingPath)">
-    Go to not-existing-page
-</a>
-
-@code{
-    [Parameter]
-    [SupplyParameterFromQuery(Name = "navigate-programmatically")]
-    public bool? NavigateProgrammatically { get; set; }
-
-    private string? _nonExistingPath;
-
-    protected override void OnInitialized()
-    {
-        _nonExistingPath = $"{NavigationManager.BaseUri}not-existing-page";
-        if (NavigateProgrammatically == true)
-        {
-            NavigationManager.NavigateTo(_nonExistingPath);
-        }
-    }
-}
+<RedirectionNotFoundComponent />
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFoundComponent.razor b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFoundComponent.razor
new file mode 100644
index 000000000000..4196c38b3655
--- /dev/null
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFoundComponent.razor
@@ -0,0 +1,26 @@
+
+@inject NavigationManager NavigationManager
+
+<h1>Original page</h1>
+
+<p id="test-info">Any content</p>
+<a id="link-to-not-existing-page" href="@(_nonExistingPath)">
+    Go to not-existing-page
+</a>
+
+@code{
+    [Parameter]
+    [SupplyParameterFromQuery(Name = "navigate-programmatically")]
+    public bool? NavigateProgrammatically { get; set; }
+
+    private string? _nonExistingPath;
+
+    protected override void OnInitialized()
+    {
+        _nonExistingPath = $"{NavigationManager.BaseUri}not-existing-page";
+        if (NavigateProgrammatically == true)
+        {
+            NavigationManager.NavigateTo(_nonExistingPath);
+        }
+    }
+}
diff --git a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFoundSSR.razor b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFoundSSR.razor
deleted file mode 100644
index a4d3fbe8f7aa..000000000000
--- a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFoundSSR.razor
+++ /dev/null
@@ -1,11 +0,0 @@
-@page "/render-not-found-ssr"
-@inject NavigationManager NavigationManager
-
-<p id="test-info">Any content</p>
-
-@code{
-    protected override void OnInitialized()
-    {
-        NavigationManager.NotFound();
-    }
-}
\ No newline at end of file

From 3b89c4b4d984ae113a263afff4c5dabb821f52c4 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Wed, 21 May 2025 17:21:33 +0200
Subject: [PATCH 04/20] Clean up tests and make them work.

---
 .../ServerRenderingTests/InteractivityTest.cs |  6 ++--
 ...omponentEndpointsNoInteractivityStartup.cs |  9 +++++-
 .../RazorComponentEndpointsStartup.cs         | 14 ++++----
 .../RedirectionNotFound-Interactive.razor     | 32 -------------------
 .../RedirectionNotFound-SSR-streaming.razor   |  2 +-
 .../NotFound/RedirectionNotFound-SSR.razor    |  2 +-
 .../NotFoundInteractiveServer.razor           |  0
 .../NotFoundInteractiveWebassembly.razor      |  0
 .../Pages/NotFound/NotFoundSSR.razor          | 11 +++++++
 .../RedirectionNotFound-Interactive.razor     | 19 +++++++++++
 .../RedirectionNotFoundComponent.razor        |  0
 .../RenderModeHelper.cs                       |  2 --
 12 files changed, 51 insertions(+), 46 deletions(-)
 delete mode 100644 src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-Interactive.razor
 rename src/Components/test/testassets/Components.WasmMinimal/Pages/{ => NotFound}/NotFoundInteractiveServer.razor (100%)
 rename src/Components/test/testassets/Components.WasmMinimal/Pages/{ => NotFound}/NotFoundInteractiveWebassembly.razor (100%)
 create mode 100644 src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/NotFoundSSR.razor
 create mode 100644 src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFound-Interactive.razor
 rename src/Components/test/testassets/{Components.TestServer/RazorComponents => Components.WasmMinimal}/Pages/NotFound/RedirectionNotFoundComponent.razor (100%)
 rename src/Components/test/testassets/{Components.TestServer => Components.WasmMinimal}/RenderModeHelper.cs (98%)

diff --git a/src/Components/test/E2ETest/ServerRenderingTests/InteractivityTest.cs b/src/Components/test/E2ETest/ServerRenderingTests/InteractivityTest.cs
index 5dec3281e98a..dd9f2a3a47e8 100644
--- a/src/Components/test/E2ETest/ServerRenderingTests/InteractivityTest.cs
+++ b/src/Components/test/E2ETest/ServerRenderingTests/InteractivityTest.cs
@@ -1418,7 +1418,7 @@ public void NavigatesWithInteractivityByRequestRedirection(bool controlFlowByExc
     [InlineData("WebAssemblyNonPrerendered")]
     public void ProgrammaticNavigationToNotExistingPathReExecutesTo404(string renderMode)
     {
-        Navigate($"{ServerPathBase}/reexecution/redirection-not-found?render-mode={renderMode}&navigate-programmatically=true");
+        Navigate($"{ServerPathBase}/reexecution/redirection-not-found?renderMode={renderMode}&navigate-programmatically=true");
         Assert404ReExecuted();
     }
 
@@ -1428,7 +1428,7 @@ public void ProgrammaticNavigationToNotExistingPathReExecutesTo404(string render
     [InlineData("WebAssemblyNonPrerendered")]
     public void LinkNavigationToNotExistingPathReExecutesTo404(string renderMode)
     {
-        Navigate($"{ServerPathBase}/reexecution/redirection-not-found?render-mode={renderMode}");
+        Navigate($"{ServerPathBase}/reexecution/redirection-not-found?renderMode={renderMode}");
         Browser.Click(By.Id("link-to-not-existing-page"));
         Assert404ReExecuted();
     }
@@ -1442,7 +1442,7 @@ public void BrowserNavigationToNotExistingPathReExecutesTo404(string renderMode)
         // non-existing path has to have re-execution middleware set up
         // so it has to have "reexecution" prefix. Otherwise middleware mapping
         // will not be activated, see configuration in Startup
-        Navigate($"{ServerPathBase}/reexecution/not-existing-page?render-mode={renderMode}");
+        Navigate($"{ServerPathBase}/reexecution/not-existing-page?renderMode={renderMode}");
         Assert404ReExecuted();
     }
 
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs
index d072d9b444b0..b7d06fcf124d 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs
@@ -50,8 +50,15 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
         {
             app.Map("/reexecution", reexecutionApp =>
             {
+                reexecutionApp.UseStaticFiles();
+                reexecutionApp.UseRouting();
                 reexecutionApp.UseStatusCodePagesWithReExecute("/not-found-reexecute", createScopeForErrors: true);
-                ConfigureSubdirPipeline(reexecutionApp, env);
+                reexecutionApp.UseRouting();
+                reexecutionApp.UseAntiforgery();
+                reexecutionApp.UseEndpoints(endpoints =>
+                {
+                    endpoints.MapRazorComponents<TRootComponent>();
+                });
             });
 
             ConfigureSubdirPipeline(app, env);
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
index 9aa6f62b2bb1..0664081e7d15 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
@@ -75,14 +75,12 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
         {
             app.Map("/reexecution", reexecutionApp =>
             {
+                reexecutionApp.UseRouting();
                 reexecutionApp.UseStatusCodePagesWithReExecute("/not-found-reexecute", createScopeForErrors: true);
-
                 reexecutionApp.UseRouting();
+
                 reexecutionApp.UseAntiforgery();
-                reexecutionApp.UseEndpoints(endpoints =>
-                {
-                    endpoints.MapRazorComponents<TRootComponent>();
-                });
+                ConfigureEndpoints(reexecutionApp, env);
             });
 
             ConfigureSubdirPipeline(app, env);
@@ -106,11 +104,15 @@ private void ConfigureSubdirPipeline(IApplicationBuilder app, IWebHostEnvironmen
         {
             if (ctx.Request.Query.ContainsKey("add-csp"))
             {
-                 ctx.Response.Headers.Add("Content-Security-Policy", "script-src 'self' 'unsafe-inline'");
+                ctx.Response.Headers.Add("Content-Security-Policy", "script-src 'self' 'unsafe-inline'");
             }
             return nxt();
         });
+        ConfigureEndpoints(app, env);
+    }
 
+    private void ConfigureEndpoints(IApplicationBuilder app, IWebHostEnvironment env)
+    {
         _ = app.UseEndpoints(endpoints =>
         {
             var contentRootStaticAssetsPath = Path.Combine(env.ContentRootPath, "Components.TestServer.staticwebassets.endpoints.json");
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-Interactive.razor b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-Interactive.razor
deleted file mode 100644
index 01351b40bb8a..000000000000
--- a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-Interactive.razor
+++ /dev/null
@@ -1,32 +0,0 @@
-@page "/redirection-not-found"
-@page "/reexecution/redirection-not-found"
-@rendermode @(RenderModeHelper.GetRenderMode(_currentRenderMode))
-@inject NavigationManager NavigationManager
-
-<PageTitle>Original page</PageTitle>
-
-<p id="test-info">Any content</p>
-<a id="link-to-not-existing-page" href="@(_nonExistingPath)">
-    Go to not-existing-page
-</a>
-
-@code{
-    [Parameter, SupplyParameterFromQuery(Name = "renderMode")]
-    public string? RenderModeStr { get; set; }
-
-    [Parameter]
-    [SupplyParameterFromQuery(Name = "navigate-programmatically")]
-    public bool? NavigateProgrammatically { get; set; }
-
-    private string? _nonExistingPath;
-    private RenderModeId _currentRenderMode => RenderModeHelper.ParseRenderMode(RenderModeStr);
-
-    protected override void OnInitialized()
-    {
-        _nonExistingPath = $"{NavigationManager.BaseUri}not-existing-page";
-        if (NavigateProgrammatically == true)
-        {
-            NavigationManager.NavigateTo(_nonExistingPath);
-        }
-    }
-}
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR-streaming.razor b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR-streaming.razor
index 07781aa37637..2f85f7f972a2 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR-streaming.razor
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR-streaming.razor
@@ -2,4 +2,4 @@
 @page "/reexecution/redirection-not-found-ssr-streaming"
 @attribute [StreamRendering(true)]
 
-<RedirectionNotFoundComponent />
+<Components.WasmMinimal.Pages.NotFound.RedirectionNotFoundComponent />
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR.razor b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR.razor
index d69ef0f4acbf..80a579a2e456 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR.razor
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR.razor
@@ -2,4 +2,4 @@
 @page "/reexecution/redirection-not-found-ssr"
 @attribute [StreamRendering(false)]
 
-<RedirectionNotFoundComponent />
+<Components.WasmMinimal.Pages.NotFound.RedirectionNotFoundComponent />
\ No newline at end of file
diff --git a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFoundInteractiveServer.razor b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/NotFoundInteractiveServer.razor
similarity index 100%
rename from src/Components/test/testassets/Components.WasmMinimal/Pages/NotFoundInteractiveServer.razor
rename to src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/NotFoundInteractiveServer.razor
diff --git a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFoundInteractiveWebassembly.razor b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/NotFoundInteractiveWebassembly.razor
similarity index 100%
rename from src/Components/test/testassets/Components.WasmMinimal/Pages/NotFoundInteractiveWebassembly.razor
rename to src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/NotFoundInteractiveWebassembly.razor
diff --git a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/NotFoundSSR.razor b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/NotFoundSSR.razor
new file mode 100644
index 000000000000..a4d3fbe8f7aa
--- /dev/null
+++ b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/NotFoundSSR.razor
@@ -0,0 +1,11 @@
+@page "/render-not-found-ssr"
+@inject NavigationManager NavigationManager
+
+<p id="test-info">Any content</p>
+
+@code{
+    protected override void OnInitialized()
+    {
+        NavigationManager.NotFound();
+    }
+}
\ No newline at end of file
diff --git a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFound-Interactive.razor b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFound-Interactive.razor
new file mode 100644
index 000000000000..461d8b6f5263
--- /dev/null
+++ b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFound-Interactive.razor
@@ -0,0 +1,19 @@
+@page "/redirection-not-found"
+@page "/reexecution/redirection-not-found"
+
+<RedirectionNotFoundComponent @rendermode="@RenderModeHelper.GetRenderMode(_renderMode)" />
+
+@code{
+    [Parameter, SupplyParameterFromQuery(Name = "renderMode")]
+    public string? RenderModeStr { get; set; }
+
+    private RenderModeId _renderMode;
+
+    protected override void OnInitialized()
+    {
+        if (!string.IsNullOrEmpty(RenderModeStr))
+        {
+            _renderMode = RenderModeHelper.ParseRenderMode(RenderModeStr);
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFoundComponent.razor b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFoundComponent.razor
similarity index 100%
rename from src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFoundComponent.razor
rename to src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFoundComponent.razor
diff --git a/src/Components/test/testassets/Components.TestServer/RenderModeHelper.cs b/src/Components/test/testassets/Components.WasmMinimal/RenderModeHelper.cs
similarity index 98%
rename from src/Components/test/testassets/Components.TestServer/RenderModeHelper.cs
rename to src/Components/test/testassets/Components.WasmMinimal/RenderModeHelper.cs
index ab1285699691..1845bddfbe22 100644
--- a/src/Components/test/testassets/Components.TestServer/RenderModeHelper.cs
+++ b/src/Components/test/testassets/Components.WasmMinimal/RenderModeHelper.cs
@@ -5,8 +5,6 @@
 using Microsoft.AspNetCore.Components;
 using Microsoft.AspNetCore.Components.Web;
 
-namespace TestServer;
-
 public static class RenderModeHelper
 {
     public static IComponentRenderMode GetRenderMode(RenderModeId renderMode)

From 217e8dd6e8e43a33a91997b48cfed0fc05843189 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Wed, 21 May 2025 18:37:17 +0200
Subject: [PATCH 05/20] Fix interactivity tests.

---
 .../Pages/NotFound/RedirectionNotFoundComponent.razor       | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFoundComponent.razor b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFoundComponent.razor
index 4196c38b3655..f441cc2768f5 100644
--- a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFoundComponent.razor
+++ b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFoundComponent.razor
@@ -4,7 +4,7 @@
 <h1>Original page</h1>
 
 <p id="test-info">Any content</p>
-<a id="link-to-not-existing-page" href="@(_nonExistingPath)">
+<a id="link-to-not-existing-page" href="@_nonExistingPath">
     Go to not-existing-page
 </a>
 
@@ -13,11 +13,11 @@
     [SupplyParameterFromQuery(Name = "navigate-programmatically")]
     public bool? NavigateProgrammatically { get; set; }
 
-    private string? _nonExistingPath;
+    private string _nonExistingPath = string.Empty;
 
     protected override void OnInitialized()
     {
-        _nonExistingPath = $"{NavigationManager.BaseUri}not-existing-page";
+        _nonExistingPath = $"{NavigationManager.BaseUri}reexecution/not-existing-page";
         if (NavigateProgrammatically == true)
         {
             NavigationManager.NavigateTo(_nonExistingPath);

From 6e3eb988a4f43f1dee072ef895311f430e3abcfa Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Thu, 22 May 2025 11:15:31 +0200
Subject: [PATCH 06/20] Remove routing sandwitch.

---
 .../RazorComponentEndpointsNoInteractivityStartup.cs            | 2 +-
 .../Components.TestServer/RazorComponentEndpointsStartup.cs     | 1 -
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs
index b7d06fcf124d..7257fafa898d 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs
@@ -51,9 +51,9 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
             app.Map("/reexecution", reexecutionApp =>
             {
                 reexecutionApp.UseStaticFiles();
-                reexecutionApp.UseRouting();
                 reexecutionApp.UseStatusCodePagesWithReExecute("/not-found-reexecute", createScopeForErrors: true);
                 reexecutionApp.UseRouting();
+                RazorComponentEndpointsStartup<TRootComponent>.UseFakeAuthState(reexecutionApp);
                 reexecutionApp.UseAntiforgery();
                 reexecutionApp.UseEndpoints(endpoints =>
                 {
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
index 0664081e7d15..ea4f7f7ad220 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
@@ -75,7 +75,6 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
         {
             app.Map("/reexecution", reexecutionApp =>
             {
-                reexecutionApp.UseRouting();
                 reexecutionApp.UseStatusCodePagesWithReExecute("/not-found-reexecute", createScopeForErrors: true);
                 reexecutionApp.UseRouting();
 

From e89fe2d369958d5c53ccb3f3a5aa19263e228952 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Thu, 22 May 2025 11:52:04 +0200
Subject: [PATCH 07/20] Trigger streaming.

---
 .../NotFound/RedirectionNotFound-SSR-streaming.razor     | 2 +-
 .../Pages/NotFound/RedirectionNotFoundComponent.razor    | 9 ++++++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR-streaming.razor b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR-streaming.razor
index 2f85f7f972a2..74374799ce04 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR-streaming.razor
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFound/RedirectionNotFound-SSR-streaming.razor
@@ -2,4 +2,4 @@
 @page "/reexecution/redirection-not-found-ssr-streaming"
 @attribute [StreamRendering(true)]
 
-<Components.WasmMinimal.Pages.NotFound.RedirectionNotFoundComponent />
+<Components.WasmMinimal.Pages.NotFound.RedirectionNotFoundComponent StartStreaming="true" />
diff --git a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFoundComponent.razor b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFoundComponent.razor
index f441cc2768f5..241052e41ed3 100644
--- a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFoundComponent.razor
+++ b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFoundComponent.razor
@@ -13,10 +13,17 @@
     [SupplyParameterFromQuery(Name = "navigate-programmatically")]
     public bool? NavigateProgrammatically { get; set; }
 
+    [Parameter]
+    public bool StartStreaming { get; set; } = false;
+
     private string _nonExistingPath = string.Empty;
 
-    protected override void OnInitialized()
+    protected override async Task OnInitializedAsync()
     {
+        if (StartStreaming)
+        {
+            await Task.Yield();
+        }
         _nonExistingPath = $"{NavigationManager.BaseUri}reexecution/not-existing-page";
         if (NavigateProgrammatically == true)
         {

From e4b89c17e3c11f29fa7d2c7fee1b4f6223fc0a44 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Thu, 22 May 2025 12:16:43 +0200
Subject: [PATCH 08/20] Templates use reexecution.

---
 .../content/BlazorWeb-CSharp/BlazorWeb-CSharp/Program.Main.cs | 4 +++-
 .../content/BlazorWeb-CSharp/BlazorWeb-CSharp/Program.cs      | 1 +
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Program.Main.cs b/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Program.Main.cs
index d37d24553867..b0b8d955cc6d 100644
--- a/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Program.Main.cs
+++ b/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Program.Main.cs
@@ -103,10 +103,12 @@ public static void Main(string[] args)
         #endif
         }
 
+        app.UseStatusCodePagesWithReExecute("/not-found", createScopeForErrors: true);
+
         #if (HasHttpsProfile)
         app.UseHttpsRedirection();
 
-        #endif
+#endif
         app.UseAntiforgery();
 
         app.MapStaticAssets();
diff --git a/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Program.cs b/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Program.cs
index 7ea8e5a50033..8eb1deacb1fa 100644
--- a/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Program.cs
+++ b/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Program.cs
@@ -96,6 +96,7 @@
     app.UseHsts();
 #endif
 }
+app.UseStatusCodePagesWithReExecute("/not-found", createScopeForErrors: true);
 
 #if (HasHttpsProfile)
 app.UseHttpsRedirection();

From fe7074f2e2ff7136c1bb0bdc0c0e50cbe961a508 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Wed, 28 May 2025 14:06:07 +0200
Subject: [PATCH 09/20] Fix templates and layout.

---
 .../Components/src/LayoutAttribute.cs         |  1 +
 .../Components/src/Routing/Router.cs          | 50 ++++++++++++++-----
 .../NoInteractivityTest.cs                    |  3 ++
 .../E2ETest/Tests/GlobalInteractivityTest.cs  |  3 ++
 .../Pages/CustomNotFoundPage.razor            |  4 --
 .../Pages/NotFound/CustomNotFoundPage.razor   |  5 ++
 .../Pages/NotFound/NotFoundLayout.razor       | 23 +++++++++
 .../BlazorWeb-CSharp.Client/_Imports.razor    |  3 ++
 .../Components/Pages/NotFound.razor           |  1 +
 .../Components/_Imports.razor                 |  2 +-
 .../ComponentsWebAssembly-CSharp/App.razor    |  4 +-
 .../Pages/NotFound.razor                      |  5 ++
 .../Templates.Tests/template-baselines.json   |  6 +++
 13 files changed, 91 insertions(+), 19 deletions(-)
 delete mode 100644 src/Components/test/testassets/Components.WasmMinimal/Pages/CustomNotFoundPage.razor
 create mode 100644 src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/CustomNotFoundPage.razor
 create mode 100644 src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/NotFoundLayout.razor
 create mode 100644 src/ProjectTemplates/Web.ProjectTemplates/content/ComponentsWebAssembly-CSharp/Pages/NotFound.razor

diff --git a/src/Components/Components/src/LayoutAttribute.cs b/src/Components/Components/src/LayoutAttribute.cs
index b7249f82c60c..30de25ca6568 100644
--- a/src/Components/Components/src/LayoutAttribute.cs
+++ b/src/Components/Components/src/LayoutAttribute.cs
@@ -36,5 +36,6 @@ public LayoutAttribute([DynamicallyAccessedMembers(Component)] Type layoutType)
     /// The type of the layout. The type must implement <see cref="IComponent"/>
     /// and must accept a parameter with the name 'Body'.
     /// </summary>
+    [DynamicallyAccessedMembers(Component)]
     public Type LayoutType { get; private set; }
 }
diff --git a/src/Components/Components/src/Routing/Router.cs b/src/Components/Components/src/Routing/Router.cs
index 2d2afadc3d39..ec3b2538317b 100644
--- a/src/Components/Components/src/Routing/Router.cs
+++ b/src/Components/Components/src/Routing/Router.cs
@@ -42,6 +42,9 @@ static readonly IReadOnlyDictionary<string, object> _emptyParametersDictionary
 
     private bool _onNavigateCalled;
 
+    [DynamicallyAccessedMembers(LinkerFlags.Component)]
+    private Type? _notFoundLayoutType;
+
     [Inject] private NavigationManager NavigationManager { get; set; }
 
     [Inject] private INavigationInterception NavigationInterception { get; set; }
@@ -156,6 +159,9 @@ public async Task SetParametersAsync(ParameterView parameters)
                 throw new InvalidOperationException($"The type {NotFoundPage.FullName} " +
                     $"does not have a {typeof(RouteAttribute).FullName} applied to it.");
             }
+
+            var layoutAttr = NotFoundPage.GetTypeInfo().GetCustomAttribute<LayoutAttribute>();
+            _notFoundLayoutType = layoutAttr?.LayoutType;
         }
 
         if (!_onNavigateCalled)
@@ -223,7 +229,7 @@ internal virtual void Refresh(bool isNavigationIntercepted)
         var relativePath = NavigationManager.ToBaseRelativePath(_locationAbsolute.AsSpan());
         var locationPathSpan = TrimQueryOrHash(relativePath);
         var locationPath = $"/{locationPathSpan}";
-        Activity? activity = null;
+        Activity? activity;
 
         // In order to avoid routing twice we check for RouteData
         if (RoutingStateProvider?.RouteData is { } endpointRouteData)
@@ -286,7 +292,7 @@ internal virtual void Refresh(bool isNavigationIntercepted)
                 // We did not find a Component that matches the route.
                 // Only show the NotFound content if the application developer programatically got us here i.e we did not
                 // intercept the navigation. In all other cases, force a browser navigation since this could be non-Blazor content.
-                _renderHandle.Render(NotFound ?? DefaultNotFoundContent);
+                RenderNotFound();
             }
             else
             {
@@ -382,23 +388,43 @@ private void OnNotFound(object sender, EventArgs args)
         if (_renderHandle.IsInitialized)
         {
             Log.DisplayingNotFound(_logger);
-            _renderHandle.Render(builder =>
+            RenderNotFound();
+        }
+    }
+
+    private void RenderNotFound()
+    {
+        _renderHandle.Render(builder =>
+        {
+            if (NotFoundPage != null)
             {
-                if (NotFoundPage != null)
+                if (_notFoundLayoutType is Type layoutType)
                 {
-                    builder.OpenComponent(0, NotFoundPage);
+                    // Directly instantiate the layout type, supplying the NotFoundPage as the Body
+                    builder.OpenComponent(0, layoutType);
+                    builder.AddAttribute(1, LayoutComponentBase.BodyPropertyName,
+                        (RenderFragment)(childBuilder =>
+                        {
+                            childBuilder.OpenComponent(2, NotFoundPage);
+                            childBuilder.CloseComponent();
+                        }));
                     builder.CloseComponent();
                 }
-                else if (NotFound != null)
-                {
-                    NotFound(builder);
-                }
                 else
                 {
-                    DefaultNotFoundContent(builder);
+                    builder.OpenComponent(0, NotFoundPage);
+                    builder.CloseComponent();
                 }
-            });
-        }
+            }
+            else if (NotFound != null)
+            {
+                NotFound(builder);
+            }
+            else
+            {
+                DefaultNotFoundContent(builder);
+            }
+        });
     }
 
     async Task IHandleAfterRender.OnAfterRenderAsync()
diff --git a/src/Components/test/E2ETest/ServerRenderingTests/NoInteractivityTest.cs b/src/Components/test/E2ETest/ServerRenderingTests/NoInteractivityTest.cs
index c7af49fc7b3f..35f7140f9170 100644
--- a/src/Components/test/E2ETest/ServerRenderingTests/NoInteractivityTest.cs
+++ b/src/Components/test/E2ETest/ServerRenderingTests/NoInteractivityTest.cs
@@ -136,6 +136,9 @@ public void CanRenderNotFoundPageNoStreaming(bool useCustomNotFoundPage)
         {
             var infoText = Browser.FindElement(By.Id("test-info")).Text;
             Assert.Contains("Welcome On Custom Not Found Page", infoText);
+            // custom page should have a custom layout
+            var aboutLink = Browser.FindElement(By.Id("about-link")).Text;
+            Assert.Contains("About", aboutLink);
         }
         else
         {
diff --git a/src/Components/test/E2ETest/Tests/GlobalInteractivityTest.cs b/src/Components/test/E2ETest/Tests/GlobalInteractivityTest.cs
index 5f91c4b684f7..0595baa95bc0 100644
--- a/src/Components/test/E2ETest/Tests/GlobalInteractivityTest.cs
+++ b/src/Components/test/E2ETest/Tests/GlobalInteractivityTest.cs
@@ -39,6 +39,9 @@ public void CanRenderNotFoundInteractive(string renderingMode, bool useCustomNot
         {
             var infoText = Browser.FindElement(By.Id("test-info")).Text;
             Assert.Contains("Welcome On Custom Not Found Page", infoText);
+            // custom page should have a custom layout
+            var aboutLink = Browser.FindElement(By.Id("about-link")).Text;
+            Assert.Contains("About", aboutLink);
         }
         else
         {
diff --git a/src/Components/test/testassets/Components.WasmMinimal/Pages/CustomNotFoundPage.razor b/src/Components/test/testassets/Components.WasmMinimal/Pages/CustomNotFoundPage.razor
deleted file mode 100644
index fc48947d6ec2..000000000000
--- a/src/Components/test/testassets/Components.WasmMinimal/Pages/CustomNotFoundPage.razor
+++ /dev/null
@@ -1,4 +0,0 @@
-@page "/render-custom-not-found-page"
-
-<h3 id="test-info">Welcome On Custom Not Found Page</h3>
-<p>Sorry, the page you are looking for does not exist.</p>
\ No newline at end of file
diff --git a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/CustomNotFoundPage.razor b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/CustomNotFoundPage.razor
new file mode 100644
index 000000000000..ed03f17c7ccb
--- /dev/null
+++ b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/CustomNotFoundPage.razor
@@ -0,0 +1,5 @@
+@page "/render-custom-not-found-page"
+@layout NotFoundLayout
+
+<h3 id="test-info">Welcome On Custom Not Found Page</h3>
+<p>Sorry, the page you are looking for does not exist.</p>
diff --git a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/NotFoundLayout.razor b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/NotFoundLayout.razor
new file mode 100644
index 000000000000..a84f973cc8ea
--- /dev/null
+++ b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/NotFoundLayout.razor
@@ -0,0 +1,23 @@
+@inherits LayoutComponentBase
+
+<div class="page">
+    <header class="top-bar">
+        <a href="https://learn.microsoft.com/aspnet/core/" target="_blank">About</a>
+    </header>
+    <main>
+        <article class="content px-4">
+            @Body
+        </article>
+    </main>
+</div>
+
+<style>
+    .top-bar {
+        background-color: #0078d4;
+        color: white;
+        padding: 10px;
+        text-align: center;
+        width: 100%;
+        box-shadow: 0px 2px 5px rgba(0, 0, 0, 0.2);
+    }
+</style>
diff --git a/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp.Client/_Imports.razor b/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp.Client/_Imports.razor
index c311ee7d72d8..6bf14edd8d56 100644
--- a/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp.Client/_Imports.razor
+++ b/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp.Client/_Imports.razor
@@ -10,3 +10,6 @@
 @using Microsoft.AspNetCore.Components.Web.Virtualization
 @using Microsoft.JSInterop
 @using BlazorWeb_CSharp.Client
+@*#if (!UseServer && UseWebAssembly && InteractiveAtRoot) -->
+@using BlazorWeb_CSharp.Client.Layout
+##endif*@
\ No newline at end of file
diff --git a/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Components/Pages/NotFound.razor b/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Components/Pages/NotFound.razor
index 52784945efc4..917ada1d2328 100644
--- a/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Components/Pages/NotFound.razor
+++ b/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Components/Pages/NotFound.razor
@@ -1,4 +1,5 @@
 @page "/not-found"
+@layout MainLayout
 
 <h3>Not Found</h3>
 <p>Sorry, the content you are looking for does not exist.</p>
\ No newline at end of file
diff --git a/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Components/_Imports.razor b/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Components/_Imports.razor
index d73d6a9c9820..a7dddbc39f32 100644
--- a/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Components/_Imports.razor
+++ b/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Components/_Imports.razor
@@ -17,6 +17,6 @@
 @using BlazorWeb_CSharp.Client.Layout
 ##endif*@
 @using BlazorWeb_CSharp.Components
-@*#if (UseServer && (!UseWebAssembly || !InteractiveAtRoot)) -->
+@*#if (UseServer || !InteractiveAtRoot) -->
 @using BlazorWeb_CSharp.Components.Layout
 ##endif*@
diff --git a/src/ProjectTemplates/Web.ProjectTemplates/content/ComponentsWebAssembly-CSharp/App.razor b/src/ProjectTemplates/Web.ProjectTemplates/content/ComponentsWebAssembly-CSharp/App.razor
index 15669dfec87b..faa98a6b8b42 100644
--- a/src/ProjectTemplates/Web.ProjectTemplates/content/ComponentsWebAssembly-CSharp/App.razor
+++ b/src/ProjectTemplates/Web.ProjectTemplates/content/ComponentsWebAssembly-CSharp/App.razor
@@ -1,7 +1,7 @@
 @*#if (NoAuth)
 <Router AppAssembly="@typeof(App).Assembly">
     <Found Context="routeData">
-        <RouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)" />
+        <RouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)" NotFoundPage="typeof(Pages.NotFound)"/>
         <FocusOnNavigate RouteData="@routeData" Selector="h1" />
     </Found>
     <NotFound>
@@ -13,7 +13,7 @@
 </Router>
 #else
 <CascadingAuthenticationState>
-    <Router AppAssembly="@typeof(App).Assembly">
+    <Router AppAssembly="@typeof(App).Assembly" NotFoundPage="typeof(Pages.NotFound)">
         <Found Context="routeData">
             <AuthorizeRouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)">
                 <NotAuthorized>
diff --git a/src/ProjectTemplates/Web.ProjectTemplates/content/ComponentsWebAssembly-CSharp/Pages/NotFound.razor b/src/ProjectTemplates/Web.ProjectTemplates/content/ComponentsWebAssembly-CSharp/Pages/NotFound.razor
new file mode 100644
index 000000000000..917ada1d2328
--- /dev/null
+++ b/src/ProjectTemplates/Web.ProjectTemplates/content/ComponentsWebAssembly-CSharp/Pages/NotFound.razor
@@ -0,0 +1,5 @@
+@page "/not-found"
+@layout MainLayout
+
+<h3>Not Found</h3>
+<p>Sorry, the content you are looking for does not exist.</p>
\ No newline at end of file
diff --git a/src/ProjectTemplates/test/Templates.Tests/template-baselines.json b/src/ProjectTemplates/test/Templates.Tests/template-baselines.json
index d8d269531f22..2d2e391f0412 100644
--- a/src/ProjectTemplates/test/Templates.Tests/template-baselines.json
+++ b/src/ProjectTemplates/test/Templates.Tests/template-baselines.json
@@ -3145,6 +3145,7 @@
         "_Imports.razor",
         "Pages/Counter.razor",
         "Pages/Home.razor",
+        "Pages/NotFound.razor",
         "Pages/Weather.razor",
         "Layout/MainLayout.razor",
         "Layout/MainLayout.razor.css",
@@ -3227,6 +3228,7 @@
         "Pages/Authentication.razor",
         "Pages/Counter.razor",
         "Pages/Home.razor",
+        "Pages/NotFound.razor",
         "Pages/Weather.razor",
         "Layout/MainLayout.razor",
         "Layout/MainLayout.razor.css",
@@ -3318,6 +3320,7 @@
         "Pages/Authentication.razor",
         "Pages/Counter.razor",
         "Pages/Home.razor",
+        "Pages/NotFound.razor",
         "Pages/Weather.razor",
         "Layout/MainLayout.razor",
         "Layout/MainLayout.razor.css",
@@ -3407,6 +3410,7 @@
         "Pages/Authentication.razor",
         "Pages/Counter.razor",
         "Pages/Home.razor",
+        "Pages/NotFound.razor",
         "Pages/Weather.razor",
         "Layout/MainLayout.razor",
         "Layout/MainLayout.razor.css",
@@ -3495,6 +3499,7 @@
         "_Imports.razor",
         "Pages/Counter.razor",
         "Pages/Home.razor",
+        "Pages/NotFound.razor",
         "Pages/Weather.razor",
         "Layout/MainLayout.razor",
         "Layout/MainLayout.razor.css",
@@ -3584,6 +3589,7 @@
         "_Imports.razor",
         "Pages/Counter.razor",
         "Pages/Home.razor",
+        "Pages/NotFound.razor",
         "Pages/Weather.razor",
         "Layout/MainLayout.razor",
         "Layout/MainLayout.razor.css",

From 1c2dcae4c7941dcc529f71741435e8fdb77caa9e Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Wed, 28 May 2025 14:38:15 +0200
Subject: [PATCH 10/20] Fix namespace.

---
 .../testassets/Components.TestServer/RazorComponents/App.razor  | 2 +-
 .../test/testassets/Components.WasmMinimal/Routes.razor         | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/App.razor b/src/Components/test/testassets/Components.TestServer/RazorComponents/App.razor
index 4418fd392d9b..ace8d627d941 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponents/App.razor
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponents/App.razor
@@ -1,5 +1,5 @@
 @using Components.TestServer.RazorComponents.Pages.Forms
-@using Components.WasmMinimal.Pages
+@using Components.WasmMinimal.Pages.NotFound
 
 @code {
     [Parameter]
diff --git a/src/Components/test/testassets/Components.WasmMinimal/Routes.razor b/src/Components/test/testassets/Components.WasmMinimal/Routes.razor
index a0807b09bf14..92f41cc8b4f1 100644
--- a/src/Components/test/testassets/Components.WasmMinimal/Routes.razor
+++ b/src/Components/test/testassets/Components.WasmMinimal/Routes.razor
@@ -1,5 +1,5 @@
 @using Microsoft.AspNetCore.Components.Routing
-@using Components.WasmMinimal.Pages
+@using Components.WasmMinimal.Pages.NotFound
 @inject NavigationManager NavigationManager
 
 @code {

From 9f6df0186411a5fff24aa51fffb03944fca4c795 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Wed, 28 May 2025 15:44:18 +0200
Subject: [PATCH 11/20] Make sure that interactive tests work only when
 interactivity is on.

---
 .../RedirectionNotFound-Interactive.razor     |  8 ++++++--
 .../RedirectionNotFoundComponent.razor        | 19 ++++++++++++-------
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFound-Interactive.razor b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFound-Interactive.razor
index 461d8b6f5263..269277bb3be6 100644
--- a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFound-Interactive.razor
+++ b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFound-Interactive.razor
@@ -1,7 +1,7 @@
 @page "/redirection-not-found"
 @page "/reexecution/redirection-not-found"
 
-<RedirectionNotFoundComponent @rendermode="@RenderModeHelper.GetRenderMode(_renderMode)" />
+<RedirectionNotFoundComponent @rendermode="@RenderModeHelper.GetRenderMode(_renderMode)" WaitForInteractivity="true"/>
 
 @code{
     [Parameter, SupplyParameterFromQuery(Name = "renderMode")]
@@ -15,5 +15,9 @@
         {
             _renderMode = RenderModeHelper.ParseRenderMode(RenderModeStr);
         }
+        else
+        {
+            throw new ArgumentException("RenderModeStr cannot be null or empty. Did you mean to redirect to /redirection-not-found-ssr?", nameof(RenderModeStr));
+        }
     }
-}
\ No newline at end of file
+}
diff --git a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFoundComponent.razor b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFoundComponent.razor
index 241052e41ed3..68df9c6e0c8c 100644
--- a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFoundComponent.razor
+++ b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/RedirectionNotFoundComponent.razor
@@ -1,12 +1,14 @@
-
-@inject NavigationManager NavigationManager
+@inject NavigationManager NavigationManager
 
-<h1>Original page</h1>
+@if (!WaitForInteractivity || RendererInfo.IsInteractive)
+{
+    <h1>Original page</h1>
 
-<p id="test-info">Any content</p>
-<a id="link-to-not-existing-page" href="@_nonExistingPath">
-    Go to not-existing-page
-</a>
+    <p id="test-info">Any content</p>
+    <a id="link-to-not-existing-page" href="@_nonExistingPath">
+        Go to not-existing-page
+    </a>
+}
 
 @code{
     [Parameter]
@@ -16,6 +18,9 @@
     [Parameter]
     public bool StartStreaming { get; set; } = false;
 
+    [Parameter]
+    public bool WaitForInteractivity { get; set; } = false;
+
     private string _nonExistingPath = string.Empty;
 
     protected override async Task OnInitializedAsync()

From b69773a8c4e99e7a44af6aba8a2112911249e55d Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Wed, 28 May 2025 16:11:59 +0200
Subject: [PATCH 12/20] Fix: link has to have ID to check if layout is
 rendered.

---
 .../Components.WasmMinimal/Pages/NotFound/NotFoundLayout.razor  | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/NotFoundLayout.razor b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/NotFoundLayout.razor
index a84f973cc8ea..14f82987bc24 100644
--- a/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/NotFoundLayout.razor
+++ b/src/Components/test/testassets/Components.WasmMinimal/Pages/NotFound/NotFoundLayout.razor
@@ -2,7 +2,7 @@
 
 <div class="page">
     <header class="top-bar">
-        <a href="https://learn.microsoft.com/aspnet/core/" target="_blank">About</a>
+        <a id="about-link" href="https://learn.microsoft.com/aspnet/core/" target="_blank">About</a>
     </header>
     <main>
         <article class="content px-4">

From f1bbf65cb69f4ffca584c0bdd3885aaadb4e15de Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Wed, 28 May 2025 17:52:38 +0200
Subject: [PATCH 13/20] Fix: Wrong placing of NotFoundPage parameter.

---
 .../content/ComponentsWebAssembly-CSharp/App.razor            | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/ProjectTemplates/Web.ProjectTemplates/content/ComponentsWebAssembly-CSharp/App.razor b/src/ProjectTemplates/Web.ProjectTemplates/content/ComponentsWebAssembly-CSharp/App.razor
index faa98a6b8b42..1bc4054ba5f8 100644
--- a/src/ProjectTemplates/Web.ProjectTemplates/content/ComponentsWebAssembly-CSharp/App.razor
+++ b/src/ProjectTemplates/Web.ProjectTemplates/content/ComponentsWebAssembly-CSharp/App.razor
@@ -1,7 +1,7 @@
 @*#if (NoAuth)
-<Router AppAssembly="@typeof(App).Assembly">
+<Router AppAssembly="@typeof(App).Assembly" NotFoundPage="typeof(Pages.NotFound)">
     <Found Context="routeData">
-        <RouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)" NotFoundPage="typeof(Pages.NotFound)"/>
+        <RouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)"/>
         <FocusOnNavigate RouteData="@routeData" Selector="h1" />
     </Found>
     <NotFound>

From a10a0fb8b85c6f45de4939bf4c778b2829265515 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Wed, 28 May 2025 17:55:57 +0200
Subject: [PATCH 14/20] Whitespace

---
 .../content/ComponentsWebAssembly-CSharp/App.razor              | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/ProjectTemplates/Web.ProjectTemplates/content/ComponentsWebAssembly-CSharp/App.razor b/src/ProjectTemplates/Web.ProjectTemplates/content/ComponentsWebAssembly-CSharp/App.razor
index 1bc4054ba5f8..1962afdd3be6 100644
--- a/src/ProjectTemplates/Web.ProjectTemplates/content/ComponentsWebAssembly-CSharp/App.razor
+++ b/src/ProjectTemplates/Web.ProjectTemplates/content/ComponentsWebAssembly-CSharp/App.razor
@@ -13,7 +13,7 @@
 </Router>
 #else
 <CascadingAuthenticationState>
-    <Router AppAssembly="@typeof(App).Assembly" NotFoundPage="typeof(Pages.NotFound)">
+    <Router AppAssembly="@typeof(App).Assembly" NotFoundPage="typeof(Pages.NotFound)" >
         <Found Context="routeData">
             <AuthorizeRouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)">
                 <NotAuthorized>

From 561c04c977026791836d65eecedb46302dd17a4d Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Thu, 29 May 2025 09:20:41 +0200
Subject: [PATCH 15/20] Empty templates should not contain `NotFound.razor`.

---
 .../content/BlazorWeb-CSharp/.template.config/template.json      | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/.template.config/template.json b/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/.template.config/template.json
index 09f28a39ffee..33be40a65c2f 100644
--- a/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/.template.config/template.json
+++ b/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/.template.config/template.json
@@ -116,6 +116,7 @@
           "exclude": [
             "BlazorWeb-CSharp/Components/Pages/Auth.*",
             "BlazorWeb-CSharp/Components/Pages/Counter.*",
+            "BlazorWeb-CSharp/Components/Pages/NotFound.*",
             "BlazorWeb-CSharp/Components/Pages/Weather.*",
             "BlazorWeb-CSharp/Components/Layout/NavMenu.*",
             "BlazorWeb-CSharp/wwwroot/lib/**",

From 8d96617a862b275ff5be2f974cc236eb9ad6347d Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Thu, 29 May 2025 09:51:47 +0200
Subject: [PATCH 16/20] Move layout import for -ai Auto from server to client
 project.

---
 .../BlazorWeb-CSharp/BlazorWeb-CSharp.Client/_Imports.razor     | 2 +-
 .../BlazorWeb-CSharp/BlazorWeb-CSharp/Components/_Imports.razor | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp.Client/_Imports.razor b/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp.Client/_Imports.razor
index 6bf14edd8d56..79c334fb2ef0 100644
--- a/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp.Client/_Imports.razor
+++ b/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp.Client/_Imports.razor
@@ -10,6 +10,6 @@
 @using Microsoft.AspNetCore.Components.Web.Virtualization
 @using Microsoft.JSInterop
 @using BlazorWeb_CSharp.Client
-@*#if (!UseServer && UseWebAssembly && InteractiveAtRoot) -->
+@*#if (UseWebAssembly && InteractiveAtRoot) -->
 @using BlazorWeb_CSharp.Client.Layout
 ##endif*@
\ No newline at end of file
diff --git a/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Components/_Imports.razor b/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Components/_Imports.razor
index a7dddbc39f32..a2d4bcbc031e 100644
--- a/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Components/_Imports.razor
+++ b/src/ProjectTemplates/Web.ProjectTemplates/content/BlazorWeb-CSharp/BlazorWeb-CSharp/Components/_Imports.razor
@@ -17,6 +17,6 @@
 @using BlazorWeb_CSharp.Client.Layout
 ##endif*@
 @using BlazorWeb_CSharp.Components
-@*#if (UseServer || !InteractiveAtRoot) -->
+@*#if ((UseServer && !UseWebAssembly) || !InteractiveAtRoot) -->
 @using BlazorWeb_CSharp.Components.Layout
 ##endif*@

From 90f6f0fd876bec8884e32808a40e79f0e51c24e4 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Thu, 29 May 2025 12:04:47 +0200
Subject: [PATCH 17/20] Feedback: use `RouteView`.

---
 .../Components/src/Routing/Router.cs          | 19 +++++--------------
 1 file changed, 5 insertions(+), 14 deletions(-)

diff --git a/src/Components/Components/src/Routing/Router.cs b/src/Components/Components/src/Routing/Router.cs
index ec3b2538317b..9e89c937b56b 100644
--- a/src/Components/Components/src/Routing/Router.cs
+++ b/src/Components/Components/src/Routing/Router.cs
@@ -398,23 +398,14 @@ private void RenderNotFound()
         {
             if (NotFoundPage != null)
             {
+                builder.OpenComponent<RouteView>(0);
+                builder.AddAttribute(1, nameof(RouteView.RouteData),
+                    new RouteData(NotFoundPage, _emptyParametersDictionary));
                 if (_notFoundLayoutType is Type layoutType)
                 {
-                    // Directly instantiate the layout type, supplying the NotFoundPage as the Body
-                    builder.OpenComponent(0, layoutType);
-                    builder.AddAttribute(1, LayoutComponentBase.BodyPropertyName,
-                        (RenderFragment)(childBuilder =>
-                        {
-                            childBuilder.OpenComponent(2, NotFoundPage);
-                            childBuilder.CloseComponent();
-                        }));
-                    builder.CloseComponent();
-                }
-                else
-                {
-                    builder.OpenComponent(0, NotFoundPage);
-                    builder.CloseComponent();
+                    builder.AddAttribute(2, nameof(RouteView.DefaultLayout), layoutType);
                 }
+                builder.CloseComponent();
             }
             else if (NotFound != null)
             {

From bdc5050e10ccff6217d167f02ad9f7bed8b594a4 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Thu, 29 May 2025 12:41:44 +0200
Subject: [PATCH 18/20] Feedback: explicit layout passing is not necessary when
 rendering with `RouteView`.

---
 src/Components/Components/src/LayoutAttribute.cs |  1 -
 src/Components/Components/src/Routing/Router.cs  | 13 +------------
 2 files changed, 1 insertion(+), 13 deletions(-)

diff --git a/src/Components/Components/src/LayoutAttribute.cs b/src/Components/Components/src/LayoutAttribute.cs
index 30de25ca6568..b7249f82c60c 100644
--- a/src/Components/Components/src/LayoutAttribute.cs
+++ b/src/Components/Components/src/LayoutAttribute.cs
@@ -36,6 +36,5 @@ public LayoutAttribute([DynamicallyAccessedMembers(Component)] Type layoutType)
     /// The type of the layout. The type must implement <see cref="IComponent"/>
     /// and must accept a parameter with the name 'Body'.
     /// </summary>
-    [DynamicallyAccessedMembers(Component)]
     public Type LayoutType { get; private set; }
 }
diff --git a/src/Components/Components/src/Routing/Router.cs b/src/Components/Components/src/Routing/Router.cs
index 9e89c937b56b..6edf8750cb36 100644
--- a/src/Components/Components/src/Routing/Router.cs
+++ b/src/Components/Components/src/Routing/Router.cs
@@ -42,9 +42,6 @@ static readonly IReadOnlyDictionary<string, object> _emptyParametersDictionary
 
     private bool _onNavigateCalled;
 
-    [DynamicallyAccessedMembers(LinkerFlags.Component)]
-    private Type? _notFoundLayoutType;
-
     [Inject] private NavigationManager NavigationManager { get; set; }
 
     [Inject] private INavigationInterception NavigationInterception { get; set; }
@@ -157,11 +154,7 @@ public async Task SetParametersAsync(ParameterView parameters)
             if (routeAttributes.Length == 0)
             {
                 throw new InvalidOperationException($"The type {NotFoundPage.FullName} " +
-                    $"does not have a {typeof(RouteAttribute).FullName} applied to it.");
-            }
-
-            var layoutAttr = NotFoundPage.GetTypeInfo().GetCustomAttribute<LayoutAttribute>();
-            _notFoundLayoutType = layoutAttr?.LayoutType;
+                    $"does not have a {typeof(RouteAttribu
         }
 
         if (!_onNavigateCalled)
@@ -401,10 +394,6 @@ private void RenderNotFound()
                 builder.OpenComponent<RouteView>(0);
                 builder.AddAttribute(1, nameof(RouteView.RouteData),
                     new RouteData(NotFoundPage, _emptyParametersDictionary));
-                if (_notFoundLayoutType is Type layoutType)
-                {
-                    builder.AddAttribute(2, nameof(RouteView.DefaultLayout), layoutType);
-                }
                 builder.CloseComponent();
             }
             else if (NotFound != null)

From 05169c907d752b9337898cac70f338a20813dd1c Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Thu, 29 May 2025 13:20:59 +0200
Subject: [PATCH 19/20] Fix misscommit.

---
 src/Components/Components/src/Routing/Router.cs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/Components/Components/src/Routing/Router.cs b/src/Components/Components/src/Routing/Router.cs
index 6edf8750cb36..51fb3fc823d2 100644
--- a/src/Components/Components/src/Routing/Router.cs
+++ b/src/Components/Components/src/Routing/Router.cs
@@ -154,7 +154,8 @@ public async Task SetParametersAsync(ParameterView parameters)
             if (routeAttributes.Length == 0)
             {
                 throw new InvalidOperationException($"The type {NotFoundPage.FullName} " +
-                    $"does not have a {typeof(RouteAttribu
+                    $"does not have a {typeof(RouteAttribute).FullName} applied to it.");
+            }
         }
 
         if (!_onNavigateCalled)

From 1e207c2f0a3934827b7f59606856a1878f66f667 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Fri, 30 May 2025 12:37:53 +0200
Subject: [PATCH 20/20] Add error pages middlewarefor reexecution + use status
 code pages on static files as well.

---
 .../RazorComponentEndpointsNoInteractivityStartup.cs       | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs
index 7257fafa898d..4520d9202397 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsNoInteractivityStartup.cs
@@ -50,8 +50,13 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
         {
             app.Map("/reexecution", reexecutionApp =>
             {
-                reexecutionApp.UseStaticFiles();
+                if (!env.IsDevelopment())
+                {
+                    app.UseExceptionHandler("/Error", createScopeForErrors: true);
+                }
+
                 reexecutionApp.UseStatusCodePagesWithReExecute("/not-found-reexecute", createScopeForErrors: true);
+                reexecutionApp.UseStaticFiles();
                 reexecutionApp.UseRouting();
                 RazorComponentEndpointsStartup<TRootComponent>.UseFakeAuthState(reexecutionApp);
                 reexecutionApp.UseAntiforgery();