private void galleryControl1_Gallery_ContextButtonCustomize(object sender, GalleryContextButtonCustomizeEventArgs e)
        {
            CheckContextButton check = e.Item as CheckContextButton;

            if (check == null)
            {
                return;
            }
            DataItem data = (DataItem)e.GalleryItem.Tag;

            check.Checked = data.IsChecked;
        }
        private void galleryControl1_Gallery_ContextButtonClick(object sender, ContextItemClickEventArgs e)
        {
            CheckContextButton check = e.Item as CheckContextButton;

            if (check == null)
            {
                return;
            }
            GalleryItem galleryItem = e.DataItem as GalleryItem;
            DataItem    data        = (DataItem)galleryItem.Tag;

            data.IsChecked = check.Checked;
        }