public IEnumerator GetEnumerator ()
{
//FIXME: write an enumerator that uses selection.GetEnumerator
// so that invalidation is write on selection changes
object [] items = new object [Count];
for (int i = 0; i < Count; i++) {
items [i] = owner.items [owner.selected_indices [i]];
}
return items.GetEnumerator ();
}