Force a client to call a method on the service?

Question

I'm wondering if there's any way to force a client to call a specific method on a duplex WCF service. My situation is this, my service implementation is going to keep a collection of subscribers. The problem with this approach is, what if the client doesn't call Subscribe()? I was thinking that in my client interface, I'd have a method called Subscribe, but that doesn't get me anywhere since the code to actually call the service can still be left out of the implementation. Is this possible?

Thanks!

Answer 1

Duplex WCF service uses WCF session so you can mark your Subscribe method with:

[OperationContract(IsInitiating=true)]
void Subscribe();

All other methods will have IsInitiating=false and because of that Subscribe method will have to be the first method called to start a new session. You can also have special method with IsTerminating=true to close the session.