Enable SPA fallback routing on server

src/Microsoft.AspNetCore.Blazor.Server/BlazorAppBuilderExtensions.cs

@@ -1,13 +1,12 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using Microsoft.AspNetCore.StaticFiles;
+using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Blazor.Server;
+using Microsoft.AspNetCore.StaticFiles;
 using Microsoft.Extensions.FileProviders;
-using System.Collections.Generic;
 using System.IO;
 using System.Net.Mime;
-using System;
 
 namespace Microsoft.AspNetCore.Builder
 {
@@ -43,19 +42,16 @@ namespace Microsoft.AspNetCore.Builder
             var config = BlazorConfig.Read(options.ClientAssemblyPath);
             var clientAppBinDir = Path.GetDirectoryName(config.SourceOutputAssemblyPath);
             var clientAppDistDir = Path.Combine(clientAppBinDir, "dist");
-            var distFileProvider = new PhysicalFileProvider(clientAppDistDir);
-
-            applicationBuilder.UseDefaultFiles(new DefaultFilesOptions
+            var distDirStaticFiles = new StaticFileOptions
             {
-                FileProvider = distFileProvider
-            });
-
-            applicationBuilder.UseStaticFiles(new StaticFileOptions
-            {
-                FileProvider = distFileProvider,
+                FileProvider = new PhysicalFileProvider(clientAppDistDir),
                 ContentTypeProvider = CreateContentTypeProvider(),
-            });
+            };
 
+            // First, match the request against files in the client app dist directory
+            applicationBuilder.UseStaticFiles(distDirStaticFiles);
+
+            // Next, match the request against static files in wwwroot
             if (!string.IsNullOrEmpty(config.WebRootPath))
             {
                 // In development, we serve the wwwroot files directly from source
@@ -67,8 +63,21 @@ namespace Microsoft.AspNetCore.Builder
                     FileProvider = new PhysicalFileProvider(config.WebRootPath)
                 });
             }
+
+            // Finally, use SPA fallback routing (serve default page for anything else,
+            // excluding /_framework/*)
+            applicationBuilder.MapWhen(IsNotFrameworkDir, childAppBuilder =>
+            {
+                childAppBuilder.UseSpa(spa =>
+                {
+                    spa.Options.DefaultPageStaticFileOptions = distDirStaticFiles;
+                });
+            });
         }
 
+        private static bool IsNotFrameworkDir(HttpContext context)
+            => !context.Request.Path.StartsWithSegments("/_framework");
+
         private static IContentTypeProvider CreateContentTypeProvider()
         {
             var result = new FileExtensionContentTypeProvider();

src/Microsoft.AspNetCore.Blazor.Server/Microsoft.AspNetCore.Blazor.Server.csproj

@@ -6,6 +6,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.AspNetCore.StaticFiles" Version="2.0.1" />
+    <PackageReference Include="Microsoft.AspNetCore.SpaServices.Extensions" Version="2.0.0-rc2-final" />
     <PackageReference Include="Microsoft.Extensions.FileProviders.Physical" Version="2.0.0" />
   </ItemGroup>