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

Activity Execution


Every activity in Windows Workflow must be in one of six states. These states are represented by the ActivityExecutionStatus enumeration: Initialized, Executing, Closed, Canceling, Compensating, and Faulting. All activities begin in the Initialized state, and all activities end in the Closed state. The possible state transitions are shown in the figure below:

There are a couple of important comments to make about this diagram. First, the only way for an activity to transition to the Closed state is for the activity to announce to the workflow runtime that it is finished executing. An activity makes this announcement by returning ActivityExecutionStatus.Closed from one of the virtual methods discussed in the next paragraph.

All other state transitions coincide with a virtual method call to an activity. For example, the runtime invokes an activity's Execute method when the activity reaches the Executing state. The runtime invokes the Cancel method when the

activity reaches...