public Poll Add(Poll poll)
        {
            var id = _polls.Max(e => e.Id) + 1;

            poll.Id = id;
            _polls.Add(poll);

            var maxQuestionId = UtilForPoll.MaxQuestionId(_polls);
            var maxAnswerId   = UtilForPoll.MaxAnswerId(_polls);

            _polls = _polls.SetIds(maxQuestionId, maxAnswerId);
            return(poll);
        }
        public Poll Update(Poll pollChanges)
        {
            var pollId = pollChanges.Id;

            foreach (var poll in _polls.Where(poll => poll.Id == pollId))
            {
                poll?.Update(pollChanges);
            }

            var maxQuestionId = UtilForPoll.MaxQuestionId(_polls);
            var maxAnswerId   = UtilForPoll.MaxAnswerId(_polls);

            _polls = _polls.SetIds(maxQuestionId, maxAnswerId);

            return(GetPoll(pollId));
        }
        public Question UpdateQuestion(Question questionChanges)
        {
            foreach (var poll in _polls)
            {
                foreach (var question in poll.Questions)
                {
                    if (question.Id == questionChanges.Id)
                    {
                        question.Update(questionChanges);
                    }
                }
            }
            var maxQuestionId = UtilForPoll.MaxQuestionId(_polls);
            var maxAnswerId   = UtilForPoll.MaxAnswerId(_polls);

            //_polls = UtilForPoll.SetIds(_polls, maxQuestionId, maxAnswerId);
            return(questionChanges);
        }