I wondering if the expanded state of nodes is supposed to be updated on postback like the normal Treeview?

Or is this left as an exercise? I will probably add this functionality - if it it is not working. The normal Treeview got an hiddenfield _ExpandState where this information is updatet in, so I will probably just use that.

To get Checkmarks to work for a postback from a button outside the treeview I had to add a ugly hack - I know this is not a solution because the events are raised at the wrong time:

        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);

            // Hack
            if (Page.IsPostBack)
            {
                TreeView treeView = Control as TreeView;
                if (treeView != null)
                {
                    TreeNodeCollection items = treeView.Nodes;
                    _checkboxIndex = 1;
                    UpdateCheckmarks(items);
                }
            }
        }