Make the sample work (dotnet#28556)

- Fix debug assert

Author: davidfowl

src/Servers/HttpSys/HttpSysServer.slnf

@@ -15,6 +15,7 @@
       "src\\Http\\Http\\src\\Microsoft.AspNetCore.Http.csproj",
       "src\\Http\\Metadata\\src\\Microsoft.AspNetCore.Metadata.csproj",
       "src\\Http\\WebUtilities\\src\\Microsoft.AspNetCore.WebUtilities.csproj",
+      "src\\Middleware\\HostFiltering\\src\\Microsoft.AspNetCore.HostFiltering.csproj",
       "src\\Servers\\Connections.Abstractions\\src\\Microsoft.AspNetCore.Connections.Abstractions.csproj",
       "src\\Servers\\HttpSys\\samples\\HotAddSample\\HotAddSample.csproj",
       "src\\Servers\\HttpSys\\samples\\QueueSharing\\QueueSharing.csproj",
@@ -24,6 +25,7 @@
       "src\\Servers\\HttpSys\\test\\FunctionalTests\\Microsoft.AspNetCore.Server.HttpSys.FunctionalTests.csproj",
       "src\\Servers\\HttpSys\\test\\Tests\\Microsoft.AspNetCore.Server.HttpSys.Tests.csproj",
       "src\\Servers\\Kestrel\\Transport.Sockets\\src\\Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets.csproj",
+      "src\\Servers\\IIS\\IIS\\src\\Microsoft.AspNetCore.Server.IIS.csproj",
       "src\\Testing\\src\\Microsoft.AspNetCore.Testing.csproj"
     ]
   }

src/Servers/HttpSys/samples/SelfHostServer/Program.cs

@@ -16,7 +16,7 @@ public static void Main(string[] args)
 
         public static IHostBuilder CreateHostBuilder(string[] args) =>
             Host.CreateDefaultBuilder(args)
-                .ConfigureWebHostDefaults(webBuilder =>
+                .ConfigureWebHost(webBuilder =>
                 {
                     webBuilder.UseStartup<Startup>()
                     .UseHttpSys(options =>

src/Servers/HttpSys/samples/SelfHostServer/SelfHostServer.csproj

@@ -12,7 +12,6 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <Reference Include="Microsoft.AspNetCore" />
     <Reference Include="Microsoft.AspNetCore.Server.HttpSys" />
     <Reference Include="Microsoft.Extensions.Hosting" />
     <Reference Include="Microsoft.Extensions.Logging.Console" />

src/Servers/HttpSys/src/MessagePump.cs

@@ -119,7 +119,7 @@ public Task StartAsync<TContext>(IHttpApplication<TContext> application, Cancell
             // else // Attaching to an existing queue, don't add a default.
 
             // Can't start twice
-            Debug.Assert(RequestContextFactory != null);
+            Debug.Assert(RequestContextFactory == null, "Start called twice!");
 
             Debug.Assert(application != null);