ASP.NET Core initialize singleton after configuring DI

Question

So let\'s say I have a singleton class instance that I register in the DI like this:

services.AddSingleton();

And let\'s s

Answer 1

I made some manager and I need to subscribe to events of the other services. I didn't like doing this in the

webBuilder.Configure (applicationBuilder => ...

I think it should be in the section

webBuilder.ConfigureServices ((context, services) => ...

So, here is my answer (test on net.core 3):

public static IHostBuilder CreateHostBuilder (string [] args) =>
    Host.CreateDefaultBuilder (args)
        .ConfigureWebHostDefaults (webBuilder =>
        {

        ...

        services.AddSingleton();

        var buildServiceProvider = services.BuildServiceProvider();
        var someSingletonService = buildServiceProvider.GetRequiredService ();

        ...
        });