Add "Named" Services Registrations

[carusology]

One of the major qualms I have had with the Microsoft dependency injection implementation is that it has a one-type / one-registration policy. If I have two implementations of IFoo, I cannot register them both simultaneously. Instead, I need to recreate them every time I need them.

StructureMap, because it is not terrible, uses the concept of "named" registrations to get around this problem. When you register an implementation of a service to an interface, you can "name" that registration with a string.

We could add this functionality to the Microsoft implementation by creating some kind of disposable dictionary of type IDictionary<string, TValue>. For each registration of TValue, we require a name, and stick it in the dictionary. Then, when the dictionary should be disposed, it disposes all of the TValue implementations that are IDisposable.

I could envision it looking something like the following:

services.AddNamedScoped<TService, TImplementation>("Name");
services.AddNamedSingleton<TService>(typeof(TImplementation), "Name");
services.AddNamedTransient(typeof(TService), Func<IServiceProvider, TImplementation>, "Name");

Behind the scenes, this would either create or update a dictionary that had a mapping of names to services that was managed by the Microsoft service provider. When the dictionary would be disposed in accordance to its scope, it disposes its values.