cad.net的undo返回操作

        /// <summary>
        /// 命令动作编组
        /// </summary>
        /// <param name="flag">true为开始编组,false为结束编组</param>
        public static void Undo(bool flag)
        {
            //获取CAD程序 
            object cadApplication = Application.AcadApplication; //  Autodesk.AutoCAD.ApplicationServices.         
            Type cadType = cadApplication.GetType();           
            object cadActiveDocument = cadType.InvokeMember("ActiveDocument", BindingFlags.GetProperty, null, cadApplication, null);
            Type dcoType = cadActiveDocument.GetType();
             
            //增加动作编组
            string undoCtl = Getvar("UNDOCTL");
            if (flag)
            {
                if (undoCtl == "8") //存在活动编组
                {
                    dcoType.InvokeMember("EndUndoMark", BindingFlags.InvokeMethod, null, cadActiveDocument, null);
                }
                dcoType.InvokeMember("StartUndoMark", BindingFlags.InvokeMethod, null, cadActiveDocument, null);
            }
            else
            {
                dcoType.InvokeMember("EndUndoMark", BindingFlags.InvokeMethod, null, cadActiveDocument, null);
            }
        }