Can't Register Instance of IStartup in Generic Host

[thefringeninja]

According to aspnet/Hosting#333 the following used to be sufficient to use an instance of an IStartup when starting kestrel:

internal static class WebHostBuilderExtensions {
  public static IWebHostBuilder UseStartup(this IWebHostBuilder builder, IStartup startup) =>
    builder.ConfigureServices(services => services.AddSingleton(startup));
}
_host = new WebHostBuilder()
  .UseKestrel()
  .UseStartup(new MyStartup(someDep))
  .Build();

However, using the new generic hosting bits, this no longer works.

_host = Host.CreateDefaultBuilder()
  .ConfigureWebHost(builder => builder
    .UseKestrel()
    .UseStartup(new MyStartup(someDep)))
  .Build();

crit: Microsoft.AspNetCore.Hosting.Diagnostics[6]
      Application startup exception
System.InvalidOperationException: No application configured. Please specify an application via IWebHostBuilder.UseStartup, IWebHostBuilder.Configure, or specifying the startup assembly via StartupAssemblyKey in the web host configuration.

[analogrelay]

To be clear, is UseStartup implemented the same way in the generic host model (by registering it in DI)? That doesn't work in generic host, we no longer use DI to resolve the startup class (the container doesn't exist yet).

[analogrelay]

dotnet/aspnetcore#11050 is tracking work on finding alternatives to IStartup in generic host.

[analogrelay]

Closing inactive discussion thread.

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