if (req.Count > 1)
            {
                for (int i = 0; i < req.Count; i++)  //外循环是循环的次数
                {
                    for (int j = req.Count - 1; j > i; j--)  //内循环是 外循环一次比较的次数
                    {

                        if ((req[i].addcs.org_schedule_id == req[j].addcs.org_schedule_id) && (req[i].addcs.org_course_type == req[j].addcs.org_course_type))
                        {
                            req.RemoveAt(j);
                        }

                    }
                }

            }

  //找一找教程网 http://www.zyiz.net/xilie-293.html
              List<AddCS>  nonDuplicateList = req.Where((x, i) =>
               req.FindLastIndex(z =>  z.addcs.org_schedule_id == x.addcs.org_schedule_id && z.addcs.org_course_type == x.addcs.org_course_type
               )
               == i).ToList();//Lambda表达式去重