I watched the first few videos at channel 9, and was wondering about this:
For example, if I'm building something like a chat program where I want to support multiple participants, one of the participants will enter a message and submit it to the service. It would then need to relay the message to all the clients. Is there any way (besides having the client periodically update or building a WCF service into your client that can trigger the update) the service can send an update to the client?