Example of a very simplistic internal message router

SimpleMessageRouter

public class SimpleRouter
{
    protected Dictionary<Type, List<Action<IEvent>>> Routes;

    public SimpleRouter()
    {
        Routes = new Dictionary<Type, List<Action<IEvent>>>();
    }

    public void Register<T>(Action<T> handler) where T: IEvent
    {
        // I've included the DelegateAdjuster code in the download, but you could just you dynamic to simplify this
        if(Routes.ContainsKey(typeof(T))) Routes[typeof(T)].Add(DelegateAdjuster.CastArgument<IEvent, T>(x => handler(x)));
        Routes[typeof(T)] = new List<Action<IEvent>> { DelegateAdjuster.CastArgument<IEvent, T>(x => handler(x)) };
    }

    public void Handle(IEvent message)
    {
        Before(message);
        foreach (Action<IEvent> action in Routes[message.GetType()])
        {
            action.Invoke(message);
        }
        After(message);
    }

    protected virtual void Before(IEvent message)
    {
    }

    protected virtual void After(IEvent message)
    {
    }
}