public Holder <User> SignIn(User user) { List <User> usersFromDb = new List <User>(); usersFromDb = _userDatabase.GetUsers(); User userFromDb = new User(); foreach (var userDb in usersFromDb) { if (userDb.Email == user.Email) { userFromDb = userDb; break; } } if (userFromDb.UserId == 0) { return(CheckUser(user, 404, "User doesn't exists")); } return(PasswordHelper.Autheticate(userFromDb.Key, userFromDb.Salt, user.Key) ? CheckUser(userFromDb, 200, "") : CheckUser(user, 400, "User invalid")); }