title: In WF4, how to define a custom activity that can be the scope of a Variable?
body: <p>When I rehost a designer, I can declare variables and their scopes. However, not all activities can be the scope of a variable. I notice Sequence, Parallel, PickBranch can be the host, but Pick, If, Delay, can't. And all of my custom activities currently cannot be the scope of a variable. What should I do to make a custom activity able to be the scope of variables?</p>