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

Using Variable in a WF program

We can use Variable temporarily to store a value when a WF program is running. In this task, we will create a WF program that prints five numbers to the console in a loop. We will use the NumberCounter variable as a number counter.

How to do it...

  1. Create a workflow project:

    Create a new Workflow Console Application under the Chapter01 solution and name the project as UseVariable.

  2. Author a workflow:

    Add a Sequence activity, click the Sequence activity, create an Int32 NumberCounter variable, and set its Scope to Sequence. Then, author the workflow as shown in the following screenshot. In the second Assign activity type NumberCounter=NumberCounter+1.

  3. Run it:

    Set UseVariable as Startup project. Press Ctrl+F5 to build and run the workflow without debugging. The application should run in a console window and print the following message:

How it works...

To make the workflow logic easy to understand, translate the workflow into C# code. It will look like:

int NumberCounter = 0;
}while (NumberCounter <= 5);

While we can use arguments to flow data into and out of a workflow, we use Variable to store data in a workflow. Every variable has its scope, and can be accessed by activities within its scope. Variable in WF4 is pretty much like variables in imperative language such as C#.

There's more...

Please note that we cannot access to the workflow variables from the outside host. WF4 variables are designed for sharing data inside the workflow instance. We can use Bookmark to access the workflow from the outside host.

See Also

  • Customizing a MyReadLine activity with Bookmark