public async Task <ActionResult <AttendeeViewModel> > GetAttendeeRandomForItemId(string itemId)
        {
            if (!await _itemRepository.ExistItemByIdAsync(itemId))
            {
                return(NotFound());
            }

            var entity = _attendeeRepository.GetAttendeeRandomForItemId(itemId);

            if (entity == null) // 清單中的參與者都獲獎了
            {
                return(NoContent());
            }

            entity.AttendeeIsAwarded = true;
            _attendeeRepository.UpdateAttendee(entity);
            _winnerRepository.CreateWinnerForItemIdAttendeeId(itemId, entity.AttendeeId, new Winner());
            var result = await _winnerRepository.SaveAsync();

            if (!result)
            {
                return(BadRequest());
            }

            var model = _mapper.Map <AttendeeViewModel>(entity);

            return(Ok(model));
        }