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

Converting a WF program instance to XAML

In real applications, we would like to write and test WF programs in imperative code, while storing, running, and transmitting workflow as an XAML string or file. In this task, we will convert a WF program instance to an XAML string.

How to do it...

  1. Create a workflow project:

    Create a new Workflow Console Application under the Chapter01 solution and name the project ConvertWFInstanceToXML. Delete the Workflow1.xaml file that is created by default.

  2. Write code to create the workflow and its host:

    Open Program.cs file and change the code as follows:

    using System;
    using System.Activities;
    using System.Activities.Statements;
    using System.Text;
    using System.Xaml;
    using System.Activities.XamlIntegration;
    using System.IO;
    namespace ConvertWFObjectToXML {
        class Program {
            static void Main(string[] args) {
                //Create a Workflow instance object
            ActivityBuilder ab = new ActivityBuilder();
                ab.Implementation = new Sequence() 
                    Activities =
                        new WriteLine{Text="Message from Workflow"}
                //Convert Workflow instance to xml string
                StringBuilder sb = new StringBuilder();
                StringWriter sw = new StringWriter(sb);
                XamlWriter xw = 
                    new XamlXmlWriter(sw, 
                                      new XamlSchemaContext()));
                XamlServices.Save(xw, ab);
  3. Run it:

    Set ConvertWFInstanceToXML 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 message as shown in the following screenshot:

Consider the following XML string reformatted from the screenshot:

<?xml version="1.0" encoding="utf-16"?>
<Activity  x:Class="{x:Null}" 
            <WriteLine Text="Hello" />

How it works...

Consider the following code line:

XamlServices.Save(xw, ab);

XamlServices provides services for the common XAML tasks of reading XAML and writing an object graph, or reading an object and writing out an XAML file. This statement reads an ActivityBuilder object and writes XAML to an XamlWriter object.

We use ActivityBuilder as an activity wrapper so that the output XAML is a loadable workflow. In other words, if we save, say, a Sequence activity to an XamlWriter directly, then the output XML workflow will be unloadable for further use.