Two Minute WF: Workflow Types

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In this Two Minute WF, I’ll tell you about the types of workflows you can run in Windows Workflow Foundation.

Out of the box, you get two types of workflow:

  • Sequential workflow
  • State machine workflow

A sequential workflow runs a lot like a flow chart and its design-time experience reflects that. (Yes, I realize that’s technically inaccurate, but from a conceptual perspective, that’s pretty much it.) Usually sequential workflows run in services or other automated processes that don’t require user interaction.

A state machine workflow is exactly what it sounds like - a state machine. You define the set of states the workflow can be in and the valid set of transitions between the states. The actions that occur in each state determine which transition to take to move to the next state. When integrating with ASP.NET, you’ll be looking at state machine workflows.

Both workflow types can be modified (within certain limits) on the fly to be dynamic and both can communicate with external services, listen for events, or evaluate rules to determine their flows. Both use the same set of activities (actions - like “if/else,” “execute code,” etc.) to perform their internal work. (I’ll do a different Two Minute WF post on activities.)

Visual Studio 2008 comes with templates that let you very easily create console applications that host either of these workflow types so you can experiment with them and decide which type is right for your application.