Inheritance: ICoreWindowFlyout
        private async void CoreFlyoutButtonClick(object sender, RoutedEventArgs e)
        {
            var flyout = new CoreWindowFlyout(new Point(50,50));
            flyout.Title = "Sign up";
            flyout.Commands.Add(new UICommand("Yes", SaveCommand, 1));
            flyout.Commands.Add(new UICommand("No", NoCommand, 2));


            IUICommand command = await flyout.ShowAsync();
        }