Get all AsClosedTypesOf registration variants from the Autofac Builder

Question

Lets assume these classes/interfaces:

public interface ICommand
{
}

public class SomeCommand : ICommand
{
}

public interface ICommandHandler where T :         


        

Answer 1

This is an interesting and tricky problem. The generics definitely add to that complexity since going non-generic would be a simple IEnumerable resolution.

But... I think I can help.

You'll take advantage of...

• The OnRegistered event in RegisterAssemblyTypes so you can look at what was actually registered.
• The OnActivating event for the bus so you can do the registration of the handlers.
• Closures to carry the list of registered handler types into the OnActivating event.
• Some fancy-schmancy reflection to create the closed generic version(s) of the RegisterHandler method on the bus.

Here's a full, working example showing how to do it. Note I had to change the ICommandBus interface for RegisterHandler a bit since it wouldn't compile for me in the originally listed form, but you should be able to adapt as needed. I ran this in ScriptCs to verify.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using Autofac;

public interface ICommand { }
public class CommandOne : ICommand { }
public class CommandTwo : ICommand { }

public interface ICommandHandler where T : ICommand
{
  void Handle(T arg);
}

public class CommandOneHandler : ICommandHandler
{
  public void Handle(CommandOne arg) { }
}

public class CommandTwoHandler : ICommandHandler
{
  public void Handle(CommandTwo arg) { }
}

public interface ICommandBus
{
  IEnumerable