MxDrawUtility mxUtility = new MxDrawUtility();

     MxDrawPoint getPt;
     MxDrawEntity ent = mxUtility.GetEntity(out getPt, "选择实体");
     if (ent == null)
         return;
     Int64 id = ent.ObjectID;
     ent.Close();
   
     MxDrawResbuf param = new MxDrawResbuf();
     param.AddObjectId(id);

     MxDrawResbuf ret = (MxDrawResbuf)axMxDrawX1.CallEx("Mx_GetGroupForEntity", param);
     if (ret.AtString(0) == "Ok")
     {
         for (int i = 1; i < ret.Count; i++)
         {
             MessageBox.Show(ret.AtString(i));
         }

     }