Replace WebHostBuilder with HostBuilder pattern in MVC folder (#62703)

Author: Copilot

src/Hosting/Hosting/src/GenericHost/GenericWebHostBuilder.cs

@@ -20,7 +20,7 @@ namespace Microsoft.AspNetCore.Hosting;
 
 internal sealed class GenericWebHostBuilder : WebHostBuilderBase, ISupportsStartup
 {
-    private object? _startupObject;
+    private const string _startupConfigName = "__UseStartup.StartupObject";
     private readonly object _startupKey = new object();
 
     private AggregateException? _hostingStartupErrors;
@@ -170,13 +170,15 @@ public IWebHostBuilder UseStartup([DynamicallyAccessedMembers(StartupLinkerOptio
         UseSetting(WebHostDefaults.ApplicationKey, startupAssemblyName);
 
         // UseStartup can be called multiple times. Only run the last one.
-        _startupObject = startupType;
+        _builder.Properties[_startupConfigName] = startupType;
 
         _builder.ConfigureServices((context, services) =>
         {
             // Run this delegate if the startup type matches
-            if (object.ReferenceEquals(_startupObject, startupType))
+            if (_builder.Properties.TryGetValue(_startupConfigName, out var startupObject) &&
+                object.ReferenceEquals(startupObject, startupType))
             {
+                _builder.Properties.Remove(_startupConfigName);
                 UseStartup(startupType, context, services);
             }
         });
@@ -193,16 +195,18 @@ public IWebHostBuilder UseStartup([DynamicallyAccessedMembers(StartupLinkerOptio
         UseSetting(WebHostDefaults.ApplicationKey, startupAssemblyName);
 
         // Clear the startup type
-        _startupObject = startupFactory;
+        _builder.Properties[_startupConfigName] = startupFactory;
 
         _builder.ConfigureServices(ConfigureStartup);
 
         [UnconditionalSuppressMessage("Trimmer", "IL2072", Justification = "Startup type created by factory can't be determined statically.")]
         void ConfigureStartup(HostBuilderContext context, IServiceCollection services)
         {
             // UseStartup can be called multiple times. Only run the last one.
-            if (object.ReferenceEquals(_startupObject, startupFactory))
+            if (_builder.Properties.TryGetValue(_startupConfigName, out var startupObject) &&
+                object.ReferenceEquals(startupObject, startupFactory))
             {
+                _builder.Properties.Remove(_startupConfigName);
                 var webHostBuilderContext = GetWebHostBuilderContext(context);
                 var instance = startupFactory(webHostBuilderContext) ?? throw new InvalidOperationException("The specified factory returned null startup instance.");
                 UseStartup(instance.GetType(), context, services, instance);
@@ -316,12 +320,14 @@ public IWebHostBuilder Configure(Action<IApplicationBuilder> configure)
         UseSetting(WebHostDefaults.ApplicationKey, startupAssemblyName);
 
         // Clear the startup type
-        _startupObject = configure;
+        _builder.Properties[_startupConfigName] = configure;
 
         _builder.ConfigureServices((context, services) =>
         {
-            if (object.ReferenceEquals(_startupObject, configure))
+            if (_builder.Properties.TryGetValue(_startupConfigName, out var startupObject) &&
+                object.ReferenceEquals(startupObject, configure))
             {
+                _builder.Properties.Remove(_startupConfigName);
                 services.Configure<GenericWebHostServiceOptions>(options =>
                 {
                     options.ConfigureApplication = configure;
@@ -339,12 +345,14 @@ public IWebHostBuilder Configure(Action<WebHostBuilderContext, IApplicationBuild
         UseSetting(WebHostDefaults.ApplicationKey, startupAssemblyName);
 
         // Clear the startup type
-        _startupObject = configure;
+        _builder.Properties[_startupConfigName] = configure;
 
         _builder.ConfigureServices((context, services) =>
         {
-            if (object.ReferenceEquals(_startupObject, configure))
+            if (_builder.Properties.TryGetValue(_startupConfigName, out var startupObject) &&
+                object.ReferenceEquals(startupObject, configure))
             {
+                _builder.Properties.Remove(_startupConfigName);
                 services.Configure<GenericWebHostServiceOptions>(options =>
                 {
                     var webhostBuilderContext = GetWebHostBuilderContext(context);

src/Hosting/Hosting/test/GenericWebHostBuilderTests.cs

@@ -2,8 +2,10 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Linq;
+using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting.Server;
 using Microsoft.AspNetCore.Hosting.Server.Features;
+using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
@@ -128,6 +130,86 @@ public void ReadsUrlsOrPorts(string urls, string httpPorts, string httpsPorts, s
         Assert.Equal(expected, string.Join(';', server.Addresses));
     }
 
+    [Fact]
+    public async Task MultipleConfigureWebHostCallsWithUseStartupLastWins()
+    {
+        var server = new TestServer();
+        
+        using var host = new HostBuilder()
+            .ConfigureWebHost(webHostBuilder =>
+            {
+                webHostBuilder
+                    .UseServer(server)
+                    .UseStartup<FirstStartup>();
+            })
+            .ConfigureWebHost(webHostBuilder =>
+            {
+                webHostBuilder
+                    .UseStartup<SecondStartup>();
+            })
+            .Build();
+
+        await host.StartAsync();
+        await AssertResponseContains(server.RequestDelegate, "SecondStartup");
+    }
+
+    [Fact]
+    public async Task MultipleConfigureWebHostCallsWithSameUseStartupOnlyRunsOne()
+    {
+        var server = new TestServer();
+
+        using var host = new HostBuilder()
+            .ConfigureWebHost(webHostBuilder =>
+            {
+                webHostBuilder
+                    .UseServer(server)
+                    .UseStartup<FirstStartup>();
+            })
+            .ConfigureWebHost(webHostBuilder =>
+            {
+                webHostBuilder
+                    .UseStartup<FirstStartup>();
+            })
+            .Build();
+
+        await host.StartAsync();
+        Assert.Single(host.Services.GetRequiredService<IEnumerable<FirstStartup>>());
+    }
+
+    private async Task AssertResponseContains(RequestDelegate app, string expectedText)
+    {
+        var httpContext = new DefaultHttpContext();
+        httpContext.Response.Body = new MemoryStream();
+        await app(httpContext);
+        httpContext.Response.Body.Seek(0, SeekOrigin.Begin);
+        var bodyText = new StreamReader(httpContext.Response.Body).ReadToEnd();
+        Assert.Contains(expectedText, bodyText);
+    }
+
+    private class FirstStartup
+    {
+        public void ConfigureServices(IServiceCollection services) { services.AddSingleton<FirstStartup>(); }
+
+        public void Configure(IApplicationBuilder app)
+        {
+            Assert.NotNull(app.ApplicationServices.GetService<FirstStartup>());
+            Assert.Null(app.ApplicationServices.GetService<SecondStartup>());
+            app.Run(context => context.Response.WriteAsync("FirstStartup"));
+        }
+    }
+
+    private class SecondStartup
+    {
+        public void ConfigureServices(IServiceCollection services) { services.AddSingleton<SecondStartup>(); }
+
+        public void Configure(IApplicationBuilder app)
+        {
+            Assert.Null(app.ApplicationServices.GetService<FirstStartup>());
+            Assert.NotNull(app.ApplicationServices.GetService<SecondStartup>());
+            app.Run(context => context.Response.WriteAsync("SecondStartup"));
+        }
+    }
+
     private class TestServer : IServer, IServerAddressesFeature
     {
         public TestServer()
@@ -139,9 +221,31 @@ public TestServer()
 
         public ICollection<string> Addresses { get; } = new List<string>();
         public bool PreferHostingUrls { get; set; }
+        public RequestDelegate RequestDelegate { get; private set; }
 
-        public Task StartAsync<TContext>(IHttpApplication<TContext> application, CancellationToken cancellationToken) => Task.CompletedTask;
-        public Task StopAsync(CancellationToken cancellationToken) => Task.CompletedTask;
         public void Dispose() { }
+
+        public Task StartAsync<TContext>(IHttpApplication<TContext> application, CancellationToken cancellationToken)
+        {
+            // For testing that uses RequestDelegate
+            RequestDelegate = async ctx =>
+            {
+                var httpContext = application.CreateContext(ctx.Features);
+                try
+                {
+                    await application.ProcessRequestAsync(httpContext);
+                }
+                catch (Exception ex)
+                {
+                    application.DisposeContext(httpContext, ex);
+                    throw;
+                }
+                application.DisposeContext(httpContext, null);
+            };
+
+            return Task.CompletedTask;
+        }
+
+        public Task StopAsync(CancellationToken cancellationToken) => Task.CompletedTask;
     }
 }

src/Hosting/Hosting/test/WebHostBuilderTests.cs

@@ -1681,11 +1681,11 @@ public void Configure(IWebHostBuilder builder)
                        // This check is required because MVC still uses the
                        // IWebHostEnvironment instance before the container is baked
 #pragma warning disable CS0618 // Type or member is obsolete
-                       var heDescriptor = services.SingleOrDefault(s => s.ServiceType == typeof(IHostingEnvironment));
+                       var heDescriptor = services.LastOrDefault(s => s.ServiceType == typeof(IHostingEnvironment));
                        Assert.NotNull(heDescriptor);
                        Assert.NotNull(heDescriptor.ImplementationInstance);
 #pragma warning restore CS0618 // Type or member is obsolete
-                       var wheDescriptor = services.SingleOrDefault(s => s.ServiceType == typeof(IWebHostEnvironment));
+                       var wheDescriptor = services.LastOrDefault(s => s.ServiceType == typeof(IWebHostEnvironment));
                        Assert.NotNull(wheDescriptor);
                        Assert.NotNull(wheDescriptor.ImplementationInstance);
                    })

src/Mvc/Mvc.Testing/src/PublicAPI.Unshipped.txt

@@ -3,3 +3,4 @@ Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.StartServer(
 Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.UseKestrel() -> void
 Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.UseKestrel(int port) -> void
 Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.UseKestrel(System.Action<Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServerOptions!>! configureKestrelOptions) -> void
+virtual Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.CreateServer(System.IServiceProvider! serviceProvider) -> Microsoft.AspNetCore.TestHost.TestServer!

src/Mvc/Mvc.Testing/src/WebApplicationFactory.cs

@@ -143,6 +143,7 @@ internal virtual WebApplicationFactory<TEntryPoint> WithWebHostBuilderCore(Actio
         var factory = new DelegatedWebApplicationFactory(
             ClientOptions,
             CreateServer,
+            CreateServer,
             CreateHost,
             CreateWebHostBuilder,
             CreateHostBuilder,
@@ -337,7 +338,10 @@ private void ConfigureHostBuilder(IHostBuilder hostBuilder)
             }
             else
             {
-                webHostBuilder.UseTestServer();
+                webHostBuilder.ConfigureServices(services =>
+                {
+                    services.AddSingleton<IServer>(CreateServer);
+                });
             }
         });
         _host = CreateHost(hostBuilder);
@@ -565,10 +569,19 @@ private static void EnsureDepsFile()
     /// <returns>The <see cref="TestServer"/> with the bootstrapped application.</returns>
     protected virtual TestServer CreateServer(IWebHostBuilder builder) => new(builder);
 
+    /// <summary>
+    /// Creates the <see cref="TestServer"/> with the <see cref="IServiceProvider"/> from the bootstrapped application.
+    /// This is only called for applications using <see cref="IHostBuilder"/>. Applications based on
+    /// <see cref="IWebHostBuilder"/> will use <see cref="CreateHost"/> instead.
+    /// </summary>
+    /// <param name="serviceProvider">The <see cref="IServiceProvider"/> from the bootstrapped application.</param>
+    /// <returns></returns>
+    protected virtual TestServer CreateServer(IServiceProvider serviceProvider) => new(serviceProvider);
+
     /// <summary>
     /// Creates the <see cref="IHost"/> with the bootstrapped application in <paramref name="builder"/>.
     /// This is only called for applications using <see cref="IHostBuilder"/>. Applications based on
-    /// <see cref="IWebHostBuilder"/> will use <see cref="CreateServer"/> instead.
+    /// <see cref="IWebHostBuilder"/> will use <see cref="CreateServer(IWebHostBuilder)"/> instead.
     /// </summary>
     /// <param name="builder">The <see cref="IHostBuilder"/> used to create the host.</param>
     /// <returns>The <see cref="IHost"/> with the bootstrapped application.</returns>
@@ -801,6 +814,7 @@ public virtual async ValueTask DisposeAsync()
     private sealed class DelegatedWebApplicationFactory : WebApplicationFactory<TEntryPoint>
     {
         private readonly Func<IWebHostBuilder, TestServer> _createServer;
+        private readonly Func<IServiceProvider, TestServer> _createServerFromServiceProvider;
         private readonly Func<IHostBuilder, IHost> _createHost;
         private readonly Func<IWebHostBuilder?> _createWebHostBuilder;
         private readonly Func<IHostBuilder?> _createHostBuilder;
@@ -810,6 +824,7 @@ private sealed class DelegatedWebApplicationFactory : WebApplicationFactory<TEnt
         public DelegatedWebApplicationFactory(
             WebApplicationFactoryClientOptions options,
             Func<IWebHostBuilder, TestServer> createServer,
+            Func<IServiceProvider, TestServer> createServerFromServiceProvider,
             Func<IHostBuilder, IHost> createHost,
             Func<IWebHostBuilder?> createWebHostBuilder,
             Func<IHostBuilder?> createHostBuilder,
@@ -819,6 +834,7 @@ public DelegatedWebApplicationFactory(
         {
             ClientOptions = new WebApplicationFactoryClientOptions(options);
             _createServer = createServer;
+            _createServerFromServiceProvider = createServerFromServiceProvider;
             _createHost = createHost;
             _createWebHostBuilder = createWebHostBuilder;
             _createHostBuilder = createHostBuilder;
@@ -829,6 +845,8 @@ public DelegatedWebApplicationFactory(
 
         protected override TestServer CreateServer(IWebHostBuilder builder) => _createServer(builder);
 
+        protected override TestServer CreateServer(IServiceProvider serviceProvider) => _createServerFromServiceProvider(serviceProvider);
+
         protected override IHost CreateHost(IHostBuilder builder) => _createHost(builder);
 
         protected override IWebHostBuilder? CreateWebHostBuilder() => _createWebHostBuilder();
@@ -846,6 +864,7 @@ internal override WebApplicationFactory<TEntryPoint> WithWebHostBuilderCore(Acti
             return new DelegatedWebApplicationFactory(
                 ClientOptions,
                 _createServer,
+                _createServerFromServiceProvider,
                 _createHost,
                 _createWebHostBuilder,
                 _createHostBuilder,

src/Mvc/perf/benchmarkapps/BasicApi/Startup.cs

@@ -11,6 +11,7 @@
 using Microsoft.AspNetCore.Authentication.JwtBearer;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
+using Microsoft.Extensions.Hosting;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Migrations;
@@ -229,25 +230,29 @@ private void DropDatabaseTables(IServiceProvider services)
 
         public static void Main(string[] args)
         {
-            var host = CreateWebHostBuilder(args)
+            using var host = CreateHost(args)
                 .Build();
 
             host.Run();
         }
 
-        public static IWebHostBuilder CreateWebHostBuilder(string[] args)
+        public static IHostBuilder CreateHost(string[] args)
         {
             var configuration = new ConfigurationBuilder()
                 .AddEnvironmentVariables()
                 .AddCommandLine(args)
                 .Build();
 
-            return new WebHostBuilder()
-                .UseKestrel()
-                .UseUrls("http://+:5000")
-                .UseConfiguration(configuration)
-                .UseContentRoot(Directory.GetCurrentDirectory())
-                .UseStartup<Startup>();
+            return new HostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                        .UseKestrel()
+                        .UseUrls("http://+:5000")
+                        .UseConfiguration(configuration)
+                        .UseContentRoot(Directory.GetCurrentDirectory())
+                        .UseStartup<Startup>();
+                });
         }
     }
 }