MyMessage : BaseMessage {}
AnotherMessage : BaseMessage { string data; }

MyMessage.Subscribe(MyMessageHandler)
AnotherMessage.Subscribe(AnotherMessageHandler)

void MyMessageHandler(MyMessage message)
{
    // code
}

void AnotherMessageHandler(AnotherMessage message)
{
    // code
}

MyMessage.Send(MyMessageInstance);
AnotherMessage.Send(AnotherMessageInstance);

// A function-style macro is used to call this method
template <typename Type, typename Caller>
void subscribe(boost::function<void(const Type&)> subscriber, boost::shared_ptr<Caller> caller)
{
    m_subscriptions[typeid(Type)].connect(Subscribers::slot_type([subscriber](const BaseMessage& message)
    {
            subscriber(static_cast<const Type&>(message));
    }).track(caller));
}

abstract class Message<MessageArgType>
{
    public delegate void Handler(MessageArgType arg);
    private event Handler subscribers;

    public void Subscribe(Handler subscriber)
    {
        subscribers += subscriber;
    }

    public void Unsubscribe(Handler subscriber)
    {
        subscribers -= subscriber;
    }

    public void Send(MessageArgType arg)
    {
        subscribers.Invoke(arg);
    }
}

WeakEventManager<EventSource, SomeEventEventArgs>
    .AddHandler(source, "SomeEvent", source_SomeEvent);

public void Subscribe(Handler subscriber)
{
     WeakEventManager<Message, MessageArgType>
         .AddHandler(this, "subscribers", subscriber);
}