I was having trouble with a FIM custom workflow with an enumerateResourcesActivity. If an object was found, the code activity would be called, but if nothing was returned, I could not figure out how to trap that.

Turns out code activities are only executed as the resources are enumerated. (Which makes sense when I think about it, but I guess I didn't feel like thinking about it that hard.)

At any rate, I added an additional code activity after the Enumerate Resources Activity and used that to check a variable to see if the code activity on the Enumerate Resources Activity had been called.

Hope that helps someone else.