Does .NET 3.5 (WCF, or other) offer any type of push notification service?
I have a server and a client. I want a service to run on the server and if x happens
Your question couldn't be any more general, but I'm going to take a guess and suggest you look at WCF callbacks.
I doubt your question relates to WPF or even WF, but you will need to elaborate if you think otherwise.