Book Image

Programming Windows Workflow Foundation: Practical WF Techniques and Examples using XAML and C#

By : Kenneth Scott Allen
Book Image

Programming Windows Workflow Foundation: Practical WF Techniques and Examples using XAML and C#

By: Kenneth Scott Allen

Overview of this book

Windows Workflow Foundation (WF) is a technology for defining, executing, and managing workflows. It is part of the .NET Framework 3.0 and will be available natively in the Windows Vista operating system. Windows Workflow Foundation might be the most significant piece of middleware to arrive on the Windows platform since COM+ and the Distributed Transaction Coordinator. The difference is, not every application needs a distributed transaction, but nearly every application does have a workflow encoded inside it. In this book, K Scott Allen, author of renowned .NET articles at www.odetocode.com, provides you with all the information needed to develop successful products with Windows Workflow. From the basics of how Windows Workflow can solve the difficult problems inherent in workflow solutions, through authoring workflows in code, learning about the base activity library in Windows Workflow and the different types of workflow provided, and on to building event-driven workflows using state machines, workflow communications, and finally rules and conditions in Windows Workflow, this book will give you the in-depth information you need. Throughout the book, an example "bug reporting" workflow system is developed, showcasing the technology and techniques used.
Table of Contents (14 chapters)
Programming Windows Workflow Foundation: Practical WF Techniques and Examples using XAML and C#
Credits
About the Author
About the Reviewer
Preface

Conditions and Rules


Two activities in Windows Workflow thrive on conditions and rules. These activities are the Policy Activity and the Conditioned Activity Group (CAG). Although we could have listed the CAG as a control flow element, the CAG doesn't control the flow of execution as much as allow it to be controlled by conditions and rules.

The ConditionedActivityGroup

The CAG is a powerful activity that can use a combination of rules and code to reach a goal. The CAG conditionally executes activities until a condition evaluates to true. Inside of the CAG is a storyboard where we can drop activities for execution (see the screenshot on the next page). The CAG associates a WhenCondition with each activity in its storyboard, and the CAG will only execute an activity if the activity's WhenCondition evaluates to true. The CAG continues to re-evaluate the WhenCondition and re-execute the storyboard activities until its own UntilCondition evaluates to true.

The WhenCondition and UntilCondition...