/// <summary>
        /// Removes the given images from the gallery.
        /// </summary>
        /// <param name="parameter">The list of images to remove, of type System.Windows.Controls.SelectedItemCollection (from ListBox SelectedItems).</param>
        public void RemoveImages(object parameter)
        {
            System.Collections.IList list   = parameter as System.Collections.IList;
            List <Photo>             photos = list.Cast <Photo>().ToList();

            foreach (Photo p in photos)
            {
                _gallery.Remove(p);
            }
        }