Disclaimer: This article assumes you already know the following: C#, WF4 and Extension Methods.
Lately I have been reading a bunch about Data, Context and Interaction (DCI) and a lot of my current project have involved using Windows Workflow Foundation (WF4). Recently I've come to the realizaion that a WF4 Activity can also be the perfect DCI context because both are basically use cases.
I've taken some sample code written by Christian Horsdal about DCI in C# and applied to to a Workflow. He's has some very good posts about DCI and C#, I'd recommend checking them out if you want to learn more.