Returning a Dataset from Workflow Foundation to ASP.NET

• Download ASP.NETwithWF source - 3.4 KB

Introduction

The code below will help you retrieve a DataSet object from a Workflow Foundation Instance synchronously using properties.

Background

This article is in contrast to all the heavy plumbing work we do in Workflow Foundation to return a Dataset.

Using the Code

Let me begin the code straight away.

• Create an Empty Solution. Add an ASP.NET project to it.
• On the Default page, Add a GridView or any other data bound control you like.
• Add another project, WWF Sequential Library to the solution.
• Add only a single Code Activity to the designer of WWF.
• Name the Handler of the CodeActivity "CallMe".
• Open your Workflow1.designer.cs file.
• Right after the class name, add a public Property with return type DataSet, name it Result.
• Open the Workflow.cs file, inside the partial class, find the method we defined CallMe, add the below code to CallMe.

  string conn = ConfigurationManager.ConnectionStrings["Database"].ConnectionString;
  SqlConnection sqlcon = new SqlConnection(conn);
  DataSet ds = new DataSet();
  SqlDataAdapter da = new SqlDataAdapter("select top 10 firstname, 
  				lastname from Employees", sqlcon); 
  da.Fill(ds);
  Result = ds;

Now, you are done with the Workflow1.cs class. After this, add appropriate ConnectionString Section to the config file to retrieve the connection string.

• Compile your Workflow Library.
• Now switch back to your ASP.NET application.
• Add Global.ascx file to it. Add the below code to the Application_Start:

  // Code that runs on application startup
  System.Workflow.Runtime.WorkflowRuntime workflowRuntime 
      = new System.Workflow.Runtime.WorkflowRuntime();
  
  System.Workflow.Runtime.Hosting.ManualWorkflowSchedulerService manualService 
      = new System.Workflow.Runtime.Hosting.ManualWorkflowSchedulerService();
  
  workflowRuntime.AddService(manualService);
  workflowRuntime.StartRuntime();
  Application["WorkflowRuntime"] = workflowRuntime;

• Now add the below code to Application_End.

  // Code that runs on application shutdown
  System.Workflow.Runtime.WorkflowRuntime workflowRuntime 
      = Application["WorkflowRuntime"] as System.Workflow.Runtime.WorkflowRuntime;
  
  workflowRuntime.StopRuntime();

• That's it. Open your Default.aspx.cs file.
• Reference the Workflow sequential Library you created before in the web application along with System.Workflow.Runtime, System.Workflow.Runtime.Hosting,System.Workflow.Activities; System.Threading, System.Data namespaces to your file.
• Copy and paste the following code to your code behind:

  public partial class _Default : System.Web.UI.Page 
  {
      WorkflowRuntime workflowRuntime;
      AutoResetEvent autoWaitHandler = new AutoResetEvent(false); 
  
      protected void Page_Load(object sender, EventArgs e)
      {
          try
          {
              workflowRuntime = Application["WorkflowRuntime"] as WorkflowRuntime;
              ManualWorkflowSchedulerService scheduler 
                 = workflowRuntime.GetService(typeof(ManualWorkflowSchedulerService)) 
                    as ManualWorkflowSchedulerService;
              workflowRuntime.WorkflowCompleted 
                  += new EventHandler<WorkflowCompletedEventArgs>
  				(workflowRuntime_WorkflowCompleted);
  
              WorkflowInstance instance 
                  = workflowRuntime.CreateWorkflow(typeof(ASPNetWorkflow.Workflow1));
              instance.Start();
  
              //execute the workflow instance synchronously on our thread.
              scheduler.RunWorkflow(instance.InstanceId);
              autoWaitHandler.WaitOne();
          }
          catch (Exception ex)
          {
              Response.Write("Error :" + ex.Message);
          }
      }
  
      void workflowRuntime_WorkflowCompleted
  		(object sender, WorkflowCompletedEventArgs e)
      {
          //Get the result from the workflow.
          if (e.OutputParameters.ContainsKey("Result"))
          {
              DataSet ds = (DataSet)e.OutputParameters["Result"];
              GridView1.DataSource = ds.Tables[0];
              GridView1.DataBind();
          }
              
          autoWaitHandler.Set();
      }
  }

That is all. Set your web application as the Start up project and run it.

History

• 21^st January, 2011: Initial post