Writing async monotouch code

So I have a method that must execute three tasks. The first task must be completed before the other two, which can be executed in parallel. This is what I have right now (modified for simplicity) ``` void facebookButtonClicked (object sender, EventArgs e) { View.Add (loadingOverlay); AppDelegate.MobileService = new MobileServiceClient ("myserverUrl", "myApiKey"); var users= AppDelegate.MobileService.GetTable<User> (); var identities= AppDelegate.MobileService .GetTable ("Identities"); AppDelegate.MobileService .LoginAsync (this, MobileServiceAuthenticationProvider.Facebook) .ContinueWith (t => { if (t.Status == TaskStatus.RanToCompletion) { AppDelegate.mobileServiceUser = t.Result; var task1 = users.InsertAsync(new User{BirthDate = DateTime.Now}); var task2 = identities.ReadAsync(""); Task.Factory.ContinueWhenAll(new Task[]{task1,task2},_=>{ if(task1.Status==TaskStatus.RanToCompletion && task2.Status== TaskStatus.RanToCompletion) { var token = task2.Result .GetArray()[0] .GetObject () .GetNamedObject ("identities") .GetNamedObject ("facebook") .GetNamedString ("accessToken"); SaveAuthorization (token); NavigationController.PushViewController (new TabBarController (), false); } }); }}); } ``` The problem is (other than Im a newb at async code) that when it tries to execute "PushViewController" I get: UIKit.UIKitThreadAccessException: UIKit Consistency error: you are calling a UIKit method that can only be invoked from the UI thread How can I refactor/modify this code to fix it? please help.