>I may have mis-understood Michels requirements but I don't see how an interface would help. In the scenario he gave which classes should implement IParser?
>It would be useful if he wanted to use a class that was not based on the Parser class to implement the ParseGetContent() method - but that is not the case. He wants to override the behaviour of ParseGetContent() in an existing instance of Parser (or one of its derived classes)

IAC, despite the fact that I have properly defined the interface in the base class, I was not able to get the proper syntax in the client to overrides the interface method. Basically, when I call the interface method from the base class, it executes the method from the class definition and never goes in the client interface method. It seems overrides is not supported in an interface. So, I came to the same conclusion that it wouldn't help me.

>But question for Michel: If the GetPage() method knows which behaviour of ParseGetContent() should be used why not just instantiate the relevant sub-class to do the work ?

I am not sure I understand this one. Can you provide additional information?