public String GetChangeHistory()
        {
            getRoleInfo();
            JObject changeHistory = teacherHelper.GetChangeHistory();

            if ((bool)changeHistory["status"])
            {
                return(changeHistory["data"].ToString(Formatting.None));
            }
            else
            {
                return(changeHistory["msg"].ToString());
            }
        }
        public String GetChangeHistory()
        {
            tid = User.Identity.GetUserId();
            TeacherHelper teacherHelper = new TeacherHelper();
            JObject       changeHistory = teacherHelper.GetChangeHistory(tid);

            if ((bool)changeHistory["status"])
            {
                return(changeHistory["data"].ToString(Formatting.None));
            }
            else
            {
                return(changeHistory["msg"].ToString());
            }
        }