Ron Jacobs has just answered an interesting question over on his blog. The question is about whether a workflow service operation can be invoked multiple times. Ron does not provide the details of the question but the example he provides implies that the implementation of the two invocations of the same service operation may be different as the same operation name is implemented twice in the workflow. This seems like a design issue as far as the service goes but the question itself is still interesting.
If we assume that the implementation of the service operation is the same (as it should be), how do we keep the service alive so that we can invoke the same method multiple times?
The answer is by using some kind of service session using WF correlation. Content correlation is my preferred option because it is independent of infrastructure concerns and does not restrict the WCF bindings available to you. I have previously posted about how to get a workflow service to create a session using content correlation.