Welcome to the Lounge

//Example RPL_WELCOME file
public interface IWelcomeReply : IReply { }

public partial class IrcBroadcaster
{
    public event EventHandler<IWelcomeReply> WelcomeEvent;

    //Since partial constructors aren't allowed the "base" IrcBroadcaster will simply call
    //partial setup methods.
    private partial SetupWelcomeMessage()
    {
        _commandMap.Add(
            MessageCommands.RPL_WELCOME, 
            msg => WelcomeEvent?.Invoke(this, new Reply(msg))
        );
    }
}

//For many other messages, there are unique parameters so they'd have an interface implementation here.
//IWelcomeReply is one of the simplest so that's not needed as Reply handles it.