Async ctp MVC4 and workflows

Question

I have the below code which calls a workflow. I am wondering if I can changed the controller to be asynchronous using the async ctp.

public ActionResult Index()
         


        

Answer 1

We can use the TAP pattern for invoking windows workflow as follows - (Details are mentioned in my blog post http://tweetycodingxp.blogspot.com/2013/06/invoke-workflow-wf-using-task-based.html)

public async Task<ActionResult> Index(string id)
{
    var wfInputArgs = new Dictionary<string, object>
    {
        ...
    };

    var wfOutputArgs = await Task<IDictionary<string, object>>.Factory.StartNew(
        () => WorkflowInvoker.Invoke(new MyWorkflow(), wfInputArgs));
    var result = wfOutputArgs["Output1"] as IEnumerable<Class1>;
    ...
    return View(model);
}

Answer 2

Derive from AsyncController instead of Controller.

EDIT: You may also be experiencing a known bug where ASP.NET MVC4 will hang if the action returns a completed Task. You can work around this bug by adding await Task.Yield(); at the top of the action method.

On an unrelated note, this code is more efficient (and shorter, too):

var workflowTask = Task.Factory.FromAsync(invoker.BeginInvoke, invoker.EndInvoke,
    input, userState);