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

Dependency Properties


The ultimate goal of a dependency property is to manage state. The dependency property is not unique to Windows Workflow; it is also present in WF's XAML sibling—Windows Presentation Foundation. A dependency property enables a handful of critical features in WF:

  • Activity property binding

  • Attached properties

  • Meta-properties

Every class that uses a dependency property will ultimately derive from the abstract DependencyObject class. Shown in the screenshot overleaf, the DependencyObject provides methods to manipulate dependency properties, like GetValue and SetValue. Also shown in the following figure is the DependencyProperty class.

This class represents the metadata that describes a dependency property, like the Name and OwnerType.

We've already seen some of these DependencyObject methods used when we created a UserName property for our custom composite activity. Let's look again at a portion of that code that the designer generated:

public String UserName
{
get
{
return ...