Tuple <ChangedAncestorInfo <TNode>, IEnumerable <TNode> > ancChangedRange() { bool rootChanged = !object.Equals(PreOldRoot, _self.Upstream().Last()); var arg = new ChangedAncestorInfo <TNode>(_self, OldParent, oldIndex, rootChanged); return(Tuple.Create(arg, _self.Levelorder())); }