Contract-First concept looks very interesting.
Please correct me here: it appeared from the demo that the Contract-First workflow service is statefull - you were able to call different methods on the workflow service and get different results. When the WCF test client invokes a service, how does WCF test client pass a session id (or workflow instance id) to the workflow service to identify the workflow instance that this message applies to? Technically, I could have several workflow instances running on the same workflow service at the same time. I'd expect WCF tester client to somehow identify which workflow instance it tries to invoke...
Could you post code sample for the Contract-First example with a walk through that explains what happens under the cover of the workflow service as it gets invoked via WCF tester?