async Task RunModalDialogForAuthentication(UIControllerFlow flow, IObservable <LoadData> listener, LoadData initiaLoadData)
{
await ThreadingHelper.SwitchToMainThreadAsync();
windowController = new WindowController(listener,
(v, f) => f == flow,
(v, f) => f != flow);
windowController.WindowStartupLocation = WindowStartupLocation.CenterOwner;
windowController.Load(initiaLoadData.View);
windowController.ShowModal();
windowController = null;
}