I have the following code:

if (cctx.IsLoading) return;

            EntitySet<Materias> entidad = (EntitySet<Materias>)sender;

            List<Materias> mats = entidad.ToList();

            CETreeView.Clear();

            //ObservableCollection<Node> nodos = new ObservableCollection<Node>();

            foreach (Materias item in mats)

            {

                Node nodoActual = new Node("" + item.IdMateria, item.Descripcion, true);

                nodoActual.Tag = item;

                nodoActual.ChildrenLoaded=false;

                nodoActual.PopulateChildren += new TreeEventHandler(Materias_NodeExpanded);

                CETreeView.Nodes.Add(nodoActual);

            }

            Cursor = Cursors.Arrow;

I want that the node reaches the Materias_NodeExpanded when i expand the node in order to get their childs (not to charge all of them from the beggining), i already tried with PopulateChildren, Expanded, Expand events but the code of Materias_NodeExpanded is not being executed. What's the right way to do it?

The problems is that when i add a new Node to the existing node all the NodeExpand Event becames null, the workaround can be (and that's the way i am doing it now to set the NodeExpand at the end of the process, so no new nodes will be in the Nodes collection and the eventhandler will not be updated to null...