Book Image

Microsoft Windows Workflow Foundation 4.0 Cookbook

By : Andrew Zhu
Book Image

Microsoft Windows Workflow Foundation 4.0 Cookbook

By: Andrew Zhu

Overview of this book

Windows Workflow Foundation 4.0 (WF) is a significant part of .NET Framework 4.0. WF makes workflow technology available to every single programmer that uses the .NET Framework 4.0. It is easy to create long running and distributed programs using WF with the right knowledge. With this book, you will discover that working with workflows is easy. This book provides both step-by-step recipes and relevant background information. It covers all the important aspects of Windows Workflow Foundation 4.0. The best thing about this book is that all recipes are based on real-world experiences of Andrew Zhu. Andrew is a global WF and BizTalk technology support engineer for Microsoft. This book covers everything you need to know, when working with workflows. Get to grips with flow control activities, messaging, and transaction processes with easy to understand steps followed by explanations. You will quickly learn to use collection and custom WF activities and WF services.You will see recipes that illustrate integration of Windows Workflow with other applications such as WPF, ASP.NET, WCF service.Lastly, you will discover how easily you can customize W4 Designer with WF rule engine and others.
Table of Contents (15 chapters)
Microsoft Windows Workflow Foundation 4.0 Cookbook
About the Author
About the Reviewers

Creating an Asynchronous HTTP Get activity

The WebRequest class enables us to make an HTTP request in code. Usually, every WebRequest call requires some time span—several seconds or even minutes. If there is only one request, we can wait for the response. But what are we going to do if we have to make more requests, say 100—every request uses several seconds, and so 100 requests will hang our program.

Then we come up with a good idea: why not use multiple threads with one request for each thread? But it is quite expensive to initialize a thread. If one is writing.NET-managed code, each thread will take up 1MB memory and so 100 threads will use up 100MB memory! Apparently, multiple threads are not an option. So what should we do? In this task, we will create a CodeActivity that can call a method asynchronously. The key is that our activity must inherit from AsyncCodeActivity (or AsyncCodeActivity<T>).

How to do it...

  1. Create the AsyncHttpGet activity:

    Add a new code file named AsyncHttpGet...