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

Working with Rules


The declarative rule conditions we've seen in the previous sections only return a value of true or false. A condition doesn't modify a workflow. A rule, on the other hand, is both a condition and a set of actions in an if-then-else form. The Rule class in Windows Workflow represents this if-then-else concept. The class diagram in the following screenshot displays classes with important relationships to the Rule class.

The first concept to notice is that the RuleSet class manages a collection of rules. The Policy activity will use the Execute method of a RuleSet to process the rule collection. We will cover the Policy activity in more detail soon.

Every Rule inside a RuleSet has a Condition property that references a single RuleCondition object. The RuleSet logic will use the Evaluate method of a RuleCondition to retrieve a value of true or false.

Every Rule maintains two collections of RuleAction objects—the ElseActions and the ThenActions. When a rule's condition evaluates...