I've got a WCF service that offers multiple lists of items of different types. The lists can be changed on the server. Every change has to be published to all clients to make sure every client has an up-to-date copy of each server list.

Currently I'm using this strategy: On login, every client receives the current status of every list. On every change, the added or removed item is sent to all clients.

The drawback is that I have to create a callback for every list, since the items are of different types. Is there a pattern I could apply? Or do I really have to duplicate code for each of the lists?