public List<TA> GetTAList()
 {
     var errors = new List<string>();
     var repository = new TARepository();
     var service = new TaService(repository);
     return service.GetTAList(ref errors);
 }
        public string InsertTa(TA ta)
        {
            var errors = new List<string>();
            var repository = new TARepository();
            var service = new TaService(repository);

            service.InsertTA(null, ref errors);
            if (errors.Count == 0)
            {
                return "ok";
            }

            return "error";
        }
        public string UpdateStudent(TA ta)
        {
            var errors = new List<string>();
            var repository = new TARepository();
            var service = new TaService(repository);

            service.UpdateTA(ta, ref errors);

            if (errors.Count == 0)
            {
                return "ok";
            }

            return "error";
        }