public async Task AddAsync(TicketSaleDto dto) { var conference = await _conferenceRepository.GetAsync(dto.ConferenceId); if (conference is null) { throw new ConferenceNotFoundException(dto.ConferenceId); } if (conference.ParticipantsLimit.HasValue) { var ticketsCount = await _ticketRepository.CountForConferenceAsync(conference.Id); if (ticketsCount + dto.Amount > conference.ParticipantsLimit) { throw new TooManyTicketsException(conference.Id); } } var ticketSale = new TicketSale(dto.ConferenceId, dto.Name, dto.Price, dto.Amount, dto.From, dto.To); _ticketSaleRepository.Add(ticketSale); await _ticketSaleRepository.UnitOfWork.SaveChangesAsync(); if (ticketSale.Amount.HasValue) { var tickets = new List <Ticket>(); for (var i = 0; i < ticketSale.Amount; i++) { var ticket = _ticketsFactory.Generate(conference.Id, ticketSale.Price, ticketSale); tickets.Add(ticket); } _ticketRepository.AddMany(tickets); await _ticketRepository.UnitOfWork.SaveChangesAsync(); } }