So, I'm writing a VSTO 3.0 Word application level add-in, and I want a custom task pane to show for some documents but not for others. Should be easy to do, right? Not so much. First, I create an extension method for the Microsoft.Office.Interop.Wo... class that examines the properties of the document that I'm using for the show/hide behavior. So far, real simple. Then, I add an event handler to the Microsoft.Office.Interop.Wo... event in which I call the exention...