In this Two Minute WF, we’ll talk about Activities.

When you create a workflow in WF, the actions that it can take are referred to as “Activities.” Think of all the things you might want to do in a workflow:

• Flow control (while loops, if/else decisions, etc.).
• Executing code.
• Handling events.
• Calling external services.

…and so on. Each of these things is an activity. In a state machine workflow, each state the workflow can be in is an activity. Even workflows proper are activities - they’re “composite activities” that contain other activities. Which activities get used in your workflow will depend on the type of workflow you’re using and your specific needs.

This simple sequential workflow shows what it might be like to do division in a workflow. Some inputs come into the workflow and are looked at to see if the user is trying to divide by zero. If so, an exception is thrown; if not, the division is done and the results are returned. Looking at the diagram, each of the “boxes” is an activity:

• The workflow itself.
• The if/else branching activity.
• Each branch inside the if/else branching activity.
• The exception-throwing activity (“divideByZeroFault”).
• The code activity that performs the division.

Windows Workflow Foundation comes with a lot of activities, found in the System.Workflow.Activities assembly, but if you don’t like the ones that come with WF, or if you have a special business need, you can create your own custom activities to reuse in your own workflows.