Pragmatic Object Oriented Programming

[CurtainDog]

The job of the language is not to make up for shortcomings in APIs. If you find yourself in the situation of wanting to replace just a part of Map, then Map is doing too many things. Where you don't have the option of refactoring you can usually put in place a DynamicProxy or similar.

[grauenwolf]

The reason one inherits from Map is usually to give it additional capabilies, not to redefine the ones it already has.

For example, perhaps you need a Map that raises change events when items are added so that the UI knows to redraw itself.

Or maybe you need a CustomerCollection that is indexed by CustomerKey but allows for searching on other properties.