Windows workflow foundation

BANGALORE, INDIA: Windows Workflow Foundation (WF) is a component of .NET framework 3.0 and 3.5 and is part of Windows platform for developers. To understand this component let's first get introduced to a workflow. Business process consists of number of activities related to app development, and specifying these activities in a series of steps is known as a workflow. WF provides a common foundation for building workflow-based app on Windows.

Design schemes in app development are always separated from actual codes to be implemented, making design schemes mere documentation after app is developed. To overcome this separation, Microsoft came out with Windows WF, which can be used in document mgmt, business cycles, or page flow.WF is easy to understand as it gives a visual representation of process and extending existing workflow is much simpler in it.

Workflow types
WF was built to support activities in a business process, now in a business process activities can be categorized into two: system related and human related. WF tries to support both these activities with following types of workflow:

Sequential workflows: used in apps where activities are executed in a defined order and path of execution is known, ie system activities.

State-machine workflows: used in apps where path of execution of activities is not predefined. Human workflow can be implemented using this type of workflow.

Implementation
In this article,we'll implement a sample sequential workflow using .NET framework 3.5 and VS 2008. This will explain how sequential workflow actually works.

We will start with creating a new project in VS 2008, in project dialog window expand Visual c#/workflow; the project type here would be sequential workflow console app, this step will bring you in workflow designer page. Use toolbox to get various types of activities, here we are using code activity, just drag and drop code activity on the designer page. Code activity will show a red exclamation mark signifying that it should be configured. Simplest way of configuring it is to double click on code activity and add display code into it as shown in this code snippet:

using System.Workflow.ComponentModel;
using System.Workflow.Runtime;
using System.Workflow.Activities;
namespace WorkFlowExample
{public partial class Workflow1 : SequentialWorkflowActivity
{private void codeActivity1_CodeHandler(object sender, EventArgs e)
{Console.WriteLine("Intro to WF");

Move to design page and add breakpoint by right clicking on code activity box. Save and start debugging this project. You will see how control moves through code activity and displays message. Now let us build a new project similar to one we just created but this time use IfElse activity to get two paths for our workflow, and depending on parameters mentioned workflow should give desired output. In a new workflow console project drag and drop IfElse activity and then add two code activities in designer view.

There would be exclamation mark on ifElceBranhAtivity1, click on it and move to properties, from the drop down box in condition property select declarative rule condition. Expand condition property and click on button that is there in front of ConditionName property. Add condition as shown in figure 2, repeat similar steps for ifElceBranhAtivity2.

Add following code snippet in code view of workflow:

string name;
int prise;
string message;
public string Name
{get { return name; }
set { name = value; }}
public int Prise
{get { return prise; }
set { prise = value; }}
public string Message
{get { return message; }}
private void codeActivity1_ExecuteCode_1(object sender, EventArgs e)
{ifElseBranchActivity1:
message = string.Format("the prise of {0} is accepted", name);}
private void codeActivity2_ExecuteCode_1(object sender, EventArgs e)
{ifElseBranchActivity2:
message = string.Format("the prise of {0} is rejected", name);}

Move to Program.cs file and replace last three lines with the following code:

int a;
string b;
Console.WriteLine("Enter product name");
b = Console.ReadLine();
Console.WriteLine("Enter prise");
a = Convert.ToInt16(Console.ReadLine());
Dictionary parameters = new Dictionary();
parameters.Add("Name", b);
parameters.Add("Prise", a);
WorkflowInstance instance = workflowRuntime.CreateWorkflow( typeofWorkflowConsoleApplication6.Workflow1), parameters);
instance.Start();
waitHandle.WaitOne();

This is done to pass parameters to workflow and also get parameters from it. We also need to edit method in WorkflowCompleted event to:

workflowRuntime.WorkflowCompleted += delegate(object sender, WorkflowCompletedEventArgs e)
{Console.WriteLine(e.OutputParameters<"Message">);
Console.ReadKey();
waitHandle.Set();};

Now go back to design view of workflow and add break points to Codeactivity1 and 2. Start debugging this workflow, you will see how control moves through the workflow design and selects path based on parameter passed in host app.

The above two programs show how code and design are integrated in a single app. Also, one can choose from no. of other activities and build custom activities.