Firstlly please forgive my poor English skill.

When I using submenu like the image I attached.The menu is expaned,But the arrow button is still "?" . And when I click the arrow button first time, The menu did not close.

I invesgate into the DropDownMenu source.The problem is because when IsActive property is true the submenu expand.But the class (open) that used to determin close/open submenu is not added to the root component.

Any suggestion without colone and modify DropDownMenu  widget? Please help!!!

        if ($root.hasClass(openClass)) { // close it
            closeRoot($root);
            // add accessibility
            $root.attr("aria-expanded", "false");
            $panel.attr("aria-hidden", "true");
            this.focus();
        } else { // open it
            openRoot($root);
            // add accessibility
            $root.attr("aria-expanded", "true");
            $panel.attr("aria-hidden", "false");
        }