void btnSavePayment_Click(object sender, RoutedEventArgs e)
        {
            List <BookingPayment> itemSource = gvwBookingPayment.ItemsSource as List <BookingPayment>;

            if (itemSource != null && itemSource.Count > 0)
            {
                List <BookingPayment> saveList = itemSource.Where(i => i.IsChanged).ToList();
                if (saveList.Count > 0)
                {
                    Globals.IsBusy = true;
                    DataServiceHelper.SaveBookingPaymentAsync(saveList, SaveBookingPaymentCompleted);
                }
            }
        }