private void OnSortClick(object sender, RoutedEventArgs e)
        {
            var sortButton = sender as Button;

            if (sortButton == null)
            {
                return;
            }

            MenuFlyout menuFlyout = DialogService.CreateInviteContactsSortMenu(this.ViewModel.AwardClass.Contacts);

            if (menuFlyout == null)
            {
                return;
            }
            menuFlyout.Placement = FlyoutPlacementMode.Bottom;
            menuFlyout.ShowAt(sortButton);
        }