private void advTree1_MouseDown(object sender, MouseEventArgs e)        {            if (e.Button == MouseButtons.Right)//判断你点的是不是右键            {                Point ClickPoint = new Point(e.X, e.Y);                Node CurrentNode =advTree1.GetNodeAt(ClickPoint);                if (CurrentNode != null)//判断你点的是不是一个节点                {                    ContextMenu menu = new System.Windows.Forms.ContextMenu();                                     MenuItem i = new MenuItem();                    i.Text = "llllll";                    menu.MenuItems.Add(i);                    CurrentNode.ContextMenu = menu;                                     advTree1.SelectedNode = CurrentNode;//选中这个节点                }            }        }