Handling WF 4.0 long running activity using TPL

Question

I created an activity which executes a web request and stores the result into the database. Usually this process takes about 1 hour and it makes workflow engine to behave abnormally. I found out that for these long running activities I should write some different code so that the workflow engine thread won't be blocked.

Studying some blogs about writing long running activities I understand that I should use Bookmark concept. But I didn't any solution using TPL and Task.

Is this code correct for handling a long running activity using Tasks?

public sealed class WebSaveActivity : NativeActivity
{
    protected override void Execute(NativeActivityContext context)
    {
        context.CreateBookmark("websave", (activityContext, bookmark, value) =>
        {

        });

        Task.Factory.StartNew(() =>
        {
            GetAndSave(); // This takes 1 hour to accomplish.
            context.RemoveBookmark("websave");
        });

    }

    protected override bool CanInduceIdle 
    {
        get
        {
            return true;
        }
    }
}

Answer 1

I just saw your related question here: How to write a long running activity to call web services in WF 4.0

Another way is to implement your activity is as an AsyncCodeActivity:

namespace MyLibrary.Activities
{
    using System;
    using System.Activities;

    public sealed class MyActivity : AsyncCodeActivity
    {
        protected override IAsyncResult BeginExecute(AsyncCodeActivityContext context, AsyncCallback callback, object state)
        {
            var delegateToLongOperation = new Func<bool>(this.LongRunningSave);
            context.UserState = delegateToLongOperation;
            return delegateToLongOperation.BeginInvoke(callback, state);
        }

        protected override void EndExecute(AsyncCodeActivityContext context, IAsyncResult result)
        {
            var longOperationDelegate = (Func<bool>) context.UserState;
            var longOperationResult = longOperationDelegate.EndInvoke(result);

            // Can continue your activity logic here.
        }

        private bool LongRunningSave()
        {
            // Logic to perform the save.
            return true;
        }
    }
}

The workflow instance stays in memory, but at the very least the workflow runtime can handle its normal scheduling tasks without one of its threads being taken up by a long running process.