Replace service registration in ASP.NET Core built-in DI container?

Question

Let us consider a service registration in Startup.ConfigureServices:

public void ConfigureServices(IServiceCollection services)
{
    services.A         


        

Answer 1

Just to add on @ilya-chumakov 's great answer, here is the same method but with support for implementation factories

public static IServiceCollection Replace(
    this IServiceCollection services,
    Func implementationFactory,
    ServiceLifetime lifetime)
    where TService : class
{
    var descriptorToRemove = services.FirstOrDefault(d => d.ServiceType == typeof(TService));

    services.Remove(descriptorToRemove);

    var descriptorToAdd = new ServiceDescriptor(typeof(TService), implementationFactory, lifetime);

    services.Add(descriptorToAdd);

    return services;
}

in case we want to use it with a factory that instantiates the service like the following sample:

var serviceProvider = 
  new ServiceCollection()
    .Replace(sp => new MyService(), ServiceLifetime.Singleto)
    .BuildServiceProvider();