Question

Let’s say you have the service:

interface ISuessService {
    Task<Thing> Thing1();
    Task<Thing> Thing2(); 
}

And I have an extension method ContinueOnUIThread, where I can do cool stuff like:

myService.Thing1().ContinueOnUIThread(_ => label.Text = "Done!");

and interact with the UI thread easily.

What is the best way to implement a new ContinueWith extension method that does this:

myService.Thing1()
  .ContinueWith(myService.Thing2())
  .ContinueOnUIThread(_ => label.Text = "Done!");

Basically starts Thing2 after Thing1 is complete, followed by a call to the UI thread.

The closest I’ve come is something like this, but I really don’t like calling Wait:

myService.Thing1()
  .ContinueWith(_ => { 
     var thing2 = myService.Thing2().Wait(); 
     return thing2.Result; 
   })
  .ContinueOnUIThread(_ => label.Text = "Done!");

Is there a clean way to do this?

PS – I don’t have .Net 4.5 so no await/async allowed – this code has to run on MonoTouch/Mono for Android so stick to 4.0

PS – note my use of _, this is just a shortcut for “I’m not really using this parameter”

Answer 1

I think what you might be looking for is the Unwrap method from System.Threading.Tasks.TaskExtensions

myService.Thing1()
.ContinueWith(_ => myService.Thing2()).Unwrap()
.ContinueOnUIThread(_ => label.Text = "Done!");