public override void AddChild(GroupNode <Element> node)
{
base.AddChild(node);
OnChanged(this);
}
public override void InsertChild(int index, GroupNode <Element> node)
{
base.InsertChild(index, node);
OnChanged(this);
}
virtual public int IndexOfChild(GroupNode <T> child)
{
return(_children.IndexOf(child));
}