How to Split ConfigureServices method (of Startup) into multiple files

Question

Separation of concerns (SoC)

Dependency injunction registrtered in ConfigureServices (method of startup class) consist of different DI's like Repository, Fluent Validations etc.

How would I go about separating DI registration into separate files (as shown below)

Answer 1

Create an extension method to hold any additional configuration you want

public static class MyExtensions {
    public static IServiceCollection AddFluentValidation(this IServiceCollection services) {

        //...add services

        return services;
    }
}

And then called in the ConfigureServices in Startup

public void ConfigureServices(IServiceCollection services) {

    //...

    services.AddFluentValidation();
    services.AddRepository();

    //...

}

The use of extension methods for populating the services collection is commonly used by the framework and 3rd party extensions.