GalleryControl内CheckContextButton複選框多選

private List<GalleryItem> checkedItems = new List<GalleryItem>();
        private void galleryControl_Gallery_ContextButtonCustomize(System.Object sender, DevExpress.XtraBars.Ribbon.Gallery.GalleryContextButtonCustomizeEventArgs e)
        {
            CheckContextButton checkItem = e.Item as CheckContextButton;
            if (checkItem != null)
                checkItem.Checked = checkedItems.Contains(e.GalleryItem);
        }
        private void galleryControl_Gallery_ContextButtonClick(object sender, DevExpress.Utils.ContextItemClickEventArgs e)
        {
            CheckContextButton checkItem = e.Item as CheckContextButton;
            GalleryItem item = (GalleryItem)e.DataItem;
            if (checkItem != null)
            {
                if ((checkItem.Checked && !checkedItems.Contains(item)))
                    checkedItems.Add(item);
                else if ((!checkItem.Checked && checkedItems.Contains(item)))
                    checkedItems.Remove(item);
            }
        }