Short version: Which changes need to be made to convert a custom workflow action, developed in VS2010, from a Sandbox to a Farm solution. Assume it is a placeholder with no logic added yet.
I have created a custom workflow action that runs fine when deployed sandboxed, but if I change the "Sandbox Solution" flag in VS2010 to False, it no longer works.
The project is successfully deployed, I can see it in Site Collection Features and use it in SharePoint Designer, but running a workflow using that activity causes an error. If I just "flip the switch" back to Sandbox = True, it works fine once again.
I have created a fresh project, with no code whatsoever in the method, and the result is the same. I suspected elements.xml needed something different, and was elated when I noticed there was a sandbox element there, but changing that from true to false only made it worse. With that setting, the activity still shows up in SharePoint Designer, but selecting it has no effect (action does not get added to the workflow).
It should be noted that my SharePoint knowledge is severely limited, so I could easily be overlooking something quite basic.