Chapter 1: Workflow Program

In this chapter we will see how to create WF program with different methods.

Loading up a WF program from an XAML file

In this task, we will run a WF program by loading it from an XAML file.

How to do it...

1. Create a Workflow project:
   Create a new Workflow Console Application under the Chapter01 solution and name the project as LoadUpWorkflowFromXML.
   
2. Author a Workflow:
   Author the Workflow1.xaml file; this Workflow will print a string to console as shown in the following screenshot:
   
   
   
3. Create code to load up the Workflow instance from an XAML string:
   Open Program.cs file and change code as follow:
   

   using System;

   using System.Activities;

   using System.Activities.Statements;

   using System.IO;

   using System.Collections;

   using System.Text;

   using System.Activities.XamlIntegration;

   namespace LoadUpWorkflowFromXML

   {

       class Program

       {

           static void Main(string[] args)

           {

               string filePath= @"C:\WF4Cookbook\Chapter01\LoadUpWFFromXML\Workflow1.xaml";

               string tempString="";

               StringBuilder xamlWFString = new StringBuilder();

               StreamReader xamlStreamReader =

                   new StreamReader(filePath);

               while (tempString != null){

                   tempString = xamlStreamReader.ReadLine();

                   if (tempString != null) {

                       xamlWFString.Append(tempString);

                   }

               }

               Activity wfInstance = ActivityXamlServices.Load(

                   new StringReader(xamlWFString.ToString()));

               WorkflowInvoker.Invoke(wfInstance);

           }

       }

   }
   
   We may need to change the file path according to our real environment.
   
4. Run it:
   Set LoadUpWorkflowFromXML 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:
   
   

How it works...

We use the following code block to read a Workflow XML string from file and store the string in xamlWFString:

string filePath= @"C:\WF4Cookbook\Chapter01\LoadUpWFFromXML\Workflow1.xaml";

string tempString="";

StringBuilder xamlWFString = new StringBuilder();

StreamReader xamlStreamReader =

    new StreamReader(filePath);

while (tempString != null){

    tempString = xamlStreamReader.ReadLine();

    if (tempString != null) {

        xamlWFString.Append(tempString);

    }

}

Then, using the following statement, ActivityXamlServices reads the XML Workflow and builds up a Workflow object graph:

Activity wfInstance = ActivityXamlServices.Load(

                new StringReader(xamlWFString.ToString()));