Host Application in Workflow

Introduction : Here I demonstrate how we call the Host method in a Workflow Application. A host application is run in the separate threads. When we build our application to provide the communication between the host application and the running workflow. The communication that occurs between client and server.

Create a Console Application :

Step 1 : Open Visual Studio 2010.

• Select File-> New-> Project.
• Select Sequential Workflow Library.
• Go to Solution Explorer and right-click.
• Select ADD-> New Item.
• Select Sequential Workflow Console Application.

Step 2 : Go to Solution Explorer and right-click in Project.

• Select Startup Project.

Step 3 : Right-click in project again.

• Select Add Reference.
• Select Project Tab.
• Click OK.

Step 4 : Go to Program.cs file and write the below code.

Code :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Workflow.Runtime;
using System.Workflow.Runtime.Hosting;
using System.Workflow.Activities;
using System.Workflow.ComponentModel;
 namespace my_ConsoleApplication1
{
  class Program
    {
        private static class4 cl4 = new class4();
      
        static void Main(string[] args)
        {
          
            using (WorkflowRuntime workflowRuntime = new WorkflowRuntime())
            {
                AutoResetEvent waitHandle = new AutoResetEvent(false);
                workflowRuntime.WorkflowCompleted += delegate(object sender, WorkflowCompletedEventArgs e) { waitHandle.Set(); };
                workflowRuntime.WorkflowTerminated += delegate(object sender, WorkflowTerminatedEventArgs e)
                {
                    Console.WriteLine(e.Exception.Message);
                    waitHandle.Set();
                };
                var dataService = new ExternalDataExchangeService();
                workflowRuntime.AddService(dataService);
                dataService.AddService(cl4);
                var parameters = new Dictionary<String, Object>();
                parameters.Add("Path", "C:\\");
                WorkflowInstance instance = workflowRuntime.CreateWorkflow(typeof(my_ConsoleApplication1.Workflow1),parameters);
                instance.Start();
                waitHandle.WaitOne();
            }
        }
    }
}

Create Interface :

Step 5 : Go to Solution Explorer and right -click on the Host project.

• Select Add -> New Item.
• Select Interface Class.
• Click Add option.
• Class.cs file open.

Code :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Workflow.Activities;
namespace my_host_application
{
    [ExternalDataExchange]
    public  interface Interface1
    {
        void ReportProgress(String fileName);
    }
}

Create Workflow :

Step 6 : Go to Workflow.cs Design option.

• Drag activity from Toolbox While, CallExternal Method activity.

Step 7 : Select View Code option.

• Write the below code.

Code :

using System;
using System.ComponentModel;
using System.ComponentModel.Design;
using System.Collections;
using System.Linq;
using System.Workflow.ComponentModel.Compiler;
using System.Workflow.ComponentModel.Serialization;
using System.Workflow.ComponentModel;
using System.Workflow.ComponentModel.Design;
using System.Workflow.Runtime;
using System.Workflow.Activities;
using System.Workflow.Activities.Rules;
using System.IO;
namespace my_host_application
{
   public sealed partial class Workflow1 : SequentialWorkflowActivity
    {
        public string currentFileName;
        private string[] files;
        private int totalFiles;
        private int currentFile;
        public Workflow1()
        {
 
            InitializeComponent();
        }

        private void SetFiles(string Path)
        {
            if (!String.IsNullOrEmpty(Path))
            {
               files = Directory.GetFiles(Path);
                totalFiles = files.Length;
                currentFile = 0;
            }
        }
        private string pathValue;
        public string Path
        {
            get { return pathValue; }
            set
            {
                pathValue = value;
                SetFiles(value);
            }
        }
        private void SetFileName(object sender, EventArgs e)
        {
            currentFileName = files[currentFile];
            currentFile++;
        }
    }
}

Step 8 : Define a condition and method for while activity.

• Select While activity and right-click.
• Define condition, Condition Name.

Step 9 : Define Method Name, Property.

• Select callExternal Method Activity.
• Go to property option.
• Give fileName and MethodName.

 Interface Implementation :

Step 10 : Go to Solution Explorer and add Class from context menu.

• Define progress condition.
• Write the below code.

Code :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using my_host_application;
using System.Workflow.Activities;
using System.Workflow.Runtime;
namespace my_ConsoleApplication1
{
    [Serializable]
    class  class4 : Interface1
    {
        public void ReportProgress(string fileName)   
     {

            Console.WriteLine("Processing file: {0}", fileName)
        }
    }
}

Step 11 : Press F6 and build the application.

Step 12 : When Workflow executes, it calls External Method activity.

• Go to Program.cs file and add the following code.

Code :

       var dataService = new ExternalDataExchangeService();
      workflowRuntime.AddService(dataService);
      dataService.AddService(cl4);
      var parameters = new Dictionary<String, Object>();
      parameters.Add("Path", "C:\\");

Step 13 : Press F5 to run the application.