protected override object SaveViewState ()
{
object baseState = null;
object itemsState = null;
baseState = base.SaveViewState ();
IStateManager manager = items as IStateManager;
if (manager != null)
itemsState = manager.SaveViewState ();
if (baseState == null && itemsState == null)
return null;
return new Pair (baseState, itemsState);
}