public string Login <T>(T entity, out T t) where T : UserModel { t = default(T); var model = LoginDataAccess.GetUserModel(entity); if (model == null || String.IsNullOrEmpty(model.UserCode)) { return("您输入的用户名不存在"); } if (model.PassWord != entity.PassWord) { return("您输入的密码不正确"); } t = model as T; return("OK"); }