public string Get(DateTime filterDate, string subject, string classDomain, int range) { if (filterDate == null) { throw new ArgumentNullException(nameof(filterDate)); } if (subject is null || subject == "-") { subject = ""; } if (classDomain is null || classDomain == "-") { classDomain = ""; } StudentDAO dao = new StudentDAO(this._config); IEnumerable <Student> list = dao.GetRoomReport(filterDate, subject, classDomain, range); return(JsonConvert.SerializeObject(list)); }