public JsonResult Create(string user_group, string user_role)
        {
            var  dao = new user_credential_dao();
            var  model_userCredential = new user_credential();
            long newUserCredentialID  = 0;

            model_userCredential.idx_user_group_id = user_group;
            model_userCredential.idx_user_role_id  = user_role;

            int result = dao.Insert(ref newUserCredentialID, model_userCredential);

            if (result == 1)
            {
                //get new info - user credential
                var newModelUserCredential = dao.ViewDetailByID(newUserCredentialID);
                var resultPara             = new {
                    status          = result,
                    id              = newModelUserCredential.id,
                    user_group_name = newModelUserCredential.user_group_name,
                    user_role_name  = newModelUserCredential.user_role_name
                };
                return(Json(resultPara, JsonRequestBehavior.AllowGet));
            }
            else
            {
                return(Json(new
                {
                    status = result
                }));
            }
        }
        public int Update(user_credential entity)
        {
            try
            {
                if (CheckExistUserCredential(entity.idx_user_role_id, entity.idx_user_group_id))
                {
                    //a userCredential already exists;
                    return(-2);
                }

                var info = db.user_credential.Find(entity.id);
                info.idx_user_role_id  = entity.idx_user_role_id;
                info.idx_user_group_id = entity.idx_user_group_id;
                db.SaveChanges();
                return(1);
            }
            catch (Exception)
            {
                return(-1);
            }
        }
        //common lib

        /// <summary>
        /// return -2 (record exist)
        /// </summary>
        /// <param name="entity"></param>
        /// <returns></returns>
        public int Insert(ref long newUserCredential, user_credential entity)
        {
            try
            {
                if (CheckExistUserCredential(entity.idx_user_role_id, entity.idx_user_group_id))
                {
                    //a userCredential already exists;
                    return(-2);
                }
                db.user_credential.Add(entity);
                db.SaveChanges();

                //return new ID after insert
                newUserCredential = entity.id;
                return(1);
            }
            catch (Exception)
            {
                return(-1);
            }
        }