static private void OnMenuOpening(object sender, CancelEventArgs e)
        {
            ContextMenuStrip           menu        = sender as ContextMenuStrip;
            MenuContext                menuContext = menu.Tag as MenuContext;
            List <MySQL.Base.MenuItem> itemsBE     = null;

            menuContext.nodes  = null;
            menuContext.rows   = null;
            menuContext.column = -1;
            if (null != menuContext.GetSelectedNodes)
            {
                menuContext.nodes = menuContext.GetSelectedNodes();
                if (null == menuContext.nodes)
                {
                    menuContext.nodes = new List <NodeIdWrapper>();
                }
                itemsBE = menuContext.GetNodesMenuItems(menuContext.nodes);
            }
            else if (null != menuContext.GetSelectedRowsCol)
            {
                menuContext.rows = menuContext.GetSelectedRowsCol(ref menuContext.column);
                if (null == menuContext.rows)
                {
                    menuContext.rows = new List <int>();
                }
                itemsBE = menuContext.GetRowsColMenuItems(menuContext.rows, menuContext.column);
            }
            menu.Items.Clear();
            if (null == itemsBE)
            {
                e.Cancel = true;
            }
            else
            {
                FillMenuItems(itemsBE, menu.Items);
                e.Cancel = false;
            }
        }