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

State Activities


All of the workflows we've examined so far have been sequential workflows. Windows Workflow also supports state-machine workflows, which is where the activities in this section come into play.

A state machine consists of a set of states. For instance, a state machine to model the workflow of a software bug might include the states open, assigned, closed, and

deferred. The workflow must always be in one of these four states. State machines are completely event driven. Only when the workflow receives an event can the current state transition to a new state. A state machine must have an initial state, and optionally an ending state. When the state machine transitions to the ending state, the workflow is complete.

State machine workflows are a good fit for modeling a process where decisions come from outside the workflow. When we make a decision, like closing a bug, we have a local communication service raise an event to the workflow. The workflow keeps track of which state...