Windows Workflow Foundation Essentials

It can be tough keeping up with all the new technologies released by Microsoft, but Windows Workflow Foundation (WF) is a technology you do not want to miss. This article demonstrates the benefits of Windows Workflow and invites you to roll up your sleeves and get started creating your first basic workflows.

If you are building applications that contain business processes and rules, you can immediately benefit from the ease of use and tremendous power of Windows Workflow diagrams, class libraries, runtime, and rules engine to get your application out the door more quickly and allow customization of rules and workflow-even after you deploy your application.

What Is Windows Workflow Foundation?

Windows Workflow Foundation (WF) is a general-purpose programming framework for creating reactive programs where business rules and flow of control are represented graphically. As you shall see, the WF programming model separates the what from the when.

.NET 3.0?

Windows Workflow Foundation is one of four technologies (along with Windows Presentation Foundation, Windows Communication Foundation, and Windows CardSpace) released by Microsoft as part of the .NET 3.0 Framework. The “3.0” designation is confusing to many developers because it seems to indicate that these technologies must be used with a new version of the .NET Framework. In reality, they work with (and currently depend on) version 2.0 of the .NET Framework as shown in Figure 1.

The problem with the 3.0 moniker is that some development shops choose not to use these new technologies because they think they need to install a new version of the .NET Framework and don’t want to make that shift in the middle of their current development cycle. So again, Microsoft has shot itself in the foot with another naming faux pas.

In reality, these 3.0 technologies are all add-on technologies that work with the .NET 2.0 Framework and Visual Studio 2005. You can use these technologies in the same way that you use third party add-ons for the .NET 2.0 Framework.

Windows Workflow Benefits

Of all the .NET 3.0 technologies, Windows Workflow is the most complete in terms of functionality and design-time experience.

From a pragmatic perspective, I don’t like to use a new technology unless it’s ready for prime time and provides tangible benefits. Windows Workflow hits the mark on both points. Here are some of the benefits you reap from WF:

• It provides a higher-level level of abstraction and visual representation of your business processes that makes them easy to understand and design-by both developers and business domain experts.
• It’s easy to change the flow and rules associated with business processes, often without having to recompile.
• WF programming encourages developers to create a core set of well-tested activities that you can reuse in multiple applications.
• Compared to their UML counterpart-Activity Diagrams-WF diagrams are first-class software artifacts that don’t become outdated and diverge from business process logic because they are the business process logic.
• The Windows Workflow runtime provides a robust, scalable environment for your workflows to execute. Workflows can be persisted to a database when they become idle (optional) and reactivated when an external stimulus occurs.

Activity-Oriented Programming

Windows Workflow introduces .NET developers to the concept of activity-oriented programming. This programming model focuses on creating application functionality by combining sets of activities to accomplish a larger business process.

As you can see in the partial workflow shown in Figure 2, a Workflow diagram contains activities such as validateProductActivity, sellProductActivity, backOrderProductActivity, and shipOrderActivity, which execute a single piece of work in a workflow.

The Windows Workflow designer allows you to add activities to a diagram and specify the flow of the work to be executed by means of conditional branching and other flow-of-control constructs that execute based on rules that you specify. This is a powerful approach that takes your application processing code “out of the weeds” and elevates it to a place where it is easy to understand and configure.

By: Kevin McNeish

Kevin McNeish is President of Oak Leaf Enterprises, Inc, and chief architect of the MM .NET Application Framework. He is a Microsoft .NET MVP and a well-know INETA speaker and trainer throughout North America and Europe including VSLive!, DevTeach (where he serves as one of the .NET chairs), SDC Netherlands, and Advisor DevCon. He is co-author of the book Professional UML with Visual Studio .NET, author of the book .NET for Visual FoxPro Developers, writes articles and has been interviewed for .NET Rocks! He spends about half his time on the road training and mentoring companies to build well-designed, high-performance .NET applications.

kevinm@oakleafsd.com