Activity is the essence of workflow; even the workflow itself is an Activity. WF4 provides some build-in activities that can be used directly in the workflow designer panel. But many times, we need to create our own activities—for example, an activity that can send e-mail to inform someone about finishing a task or any other important thing. To define our own activity, we should write a class that implements the root abstract Activity or one of its predefined subclasses.
The following is the activity modeling class hierarchy diagram:

This chapter intends to provide readers not only with some additional activities besides the built-in activities, but also with some concepts on how to build our own activities.
Before moving ahead, please create two projects. The first is the ActivityLibrary project named ActivityLibrary
.

The other is the Workflow Console Application named WorkflowConsoleApp
.

Delete Workflow1.xaml
, which is created by default. We will use these two projects throughout...