Implementing a nested asynch “call stack” scenario in .NET

static void AsyncHelp<T>(Func<T> f, Action<Exception> econt, Action<T> cont) {
  var t = new Thread((_) => {
    try {
      var res = f();
      System.Windows.Deployment.Current.Dispatcher.BeginInvoke(() => cont(res));
    } catch (Exception ex) {
      System.Windows.Deployment.Current.Dispatcher.BeginInvoke(() => econt(ex));
    }
  });
  t.Start();
}

some_handler() {
  var id = mytextbox.Text; // Save from UI to local
  AsyncHelp(
    () => GetBla(id),
    bla => result.Text = bla.ToString(), // This is safe cause it's dispatched
    ex => error.Text = ex.ToString()
  );
}

Exception ex;
Result r;
var mre = new ManualResetEvent(false);
myService.OnGetBlaCompleted += (_, e) => {
  ex = e.Error;
  r = e.Result;
  mre.Set();
}
myService.GetBlaAsync(id);
mre.WaitOne();
if (ex != null) throw ex;
// and so on