I finally got an example working where I am using a pure XAML (no code) workflow definition and also using a base class. This took a bit of research and filling in the blanks. I was surprised that Visual Studio doesn't seem to support the XAML-only stuff... sigh. And when I got is working, the designer refused to display it, so I have to stick to the XML Editor going forwards. (I haven't checked the 3.5 fixes yet, xfingers!) First I created the workflow custom base class as a csharp class, I created ......