// notification that a subgroup has become non-empty
void OnSubgroupBecameNonEmpty(EmptyGroupItem groupItem, CollectionViewGroup group)
{
// Discard placeholder container.
UnlinkContainerFromItem(groupItem, group);
if (_emptyGroupItems != null)
_emptyGroupItems.Remove(groupItem);
// inform layout as if the group just got added
if (ItemsChanged != null)
{
GeneratorPosition position = PositionFromIndex(ItemsInternal.IndexOf(group));
ItemsChanged(this, new ItemsChangedEventArgs(NotifyCollectionChangedAction.Add, position, 1, 0));
}
}
// create an empty-group placeholder item
void AddEmptyGroupItem(CollectionViewGroup group)
{
EmptyGroupItem emptyGroupItem = new EmptyGroupItem();
LinkContainerToItem(emptyGroupItem, group);
emptyGroupItem.SetGenerator(new ItemContainerGenerator(this, emptyGroupItem));
// add it to the list of placeholder items (this keeps it from being GC'd)
if (_emptyGroupItems == null)
_emptyGroupItems = new ArrayList();
_emptyGroupItems.Add(emptyGroupItem);
}