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 Composition


Let's return to the bug-tracking workflow we used in Chapter 4 to see if a custom activity can help us in building a bug-tracking application. The bug-tracking workflow is needed to request additional documentation for a bug. To request this documentation, the workflow communicates with a local service we built in Chapter 4 that implements the following interface:

[ExternalDataExchange]
interface IBugService
{
bool RequestUpload(Guid id, string userName);
event EventHandler<UploadCompletedEventArgs> UploadCompleted;
}

A workflow that needs documentation would first use a CallExternalMethod activity to invoke the RequestUpload method. Immediately afterwards, the workflow would use a HandleExternalEvent activity to wait for an UploadCompleted event. We need to insert and configure both of these activities into every workflow that might request an upload. Our goal is to replace these two activities with a single activity we customize for the job.

To get started, we...