Question

Suppose I have a baseclass called IMessage, and lots of derived message classes.

In my program I have one method that receives all messages :

void ReceiveMessage(IMessage message)
{
}

and I’d like to call a specific method for each type of message.
It would be great if I could do :

void ReceiveMessage(IMessage message)
{
    HandleMessage(message);
}

void HandleMessage(DummyMessage message)
{
    Blah;
}

void HandleMessage(SillyMessage message)
{
    Yuk;
}

..but apparently “we ain’t going out like that“.

So how would I go about implementing specific handlers for specific messages, being called from a single messagehandler ?

Answer 1

The classic way to handle this type of situation is via the Visitor pattern.

That being said, you can actually handle this a bit easier in C# via dynamic, like so:

void ReceiveMessage(IMessage message)
{
    dynamic specificMessage = message;
    this.HandleMessage(specificMessage):
}

The dynamic binding engine will find, at runtime, the “best” match for your specific message type, and route the call to the appropriate method.