public AchievementUser[] ListAchievementUsers()
        {
            var expression   = new AchievementUserWithUserAndAchievementExpression();
            var achievements = _repository.List <AchievementUser>(expression);

            return(achievements.ToArray());
        }
        public AchievementUser GetAchievementUserById(string achievementUserId)
        {
            var expression = new AchievementUserWithUserAndAchievementExpression(achievementUserId);
            var model      = _repository.GetBy <AchievementUser>(expression);

            return(model);
        }