public List<Message> GetMessages(String chatHash, Int32? count, Int32? lastMessageId, String order)
        {
            if (String.IsNullOrEmpty(chatHash))
                return null;

            IQueryable<Message> query = _messageRepository.GetAll()
                    .Where(x => x.Chat.Hash == chatHash)
                    .Include(x => x.User)
                    .Include(x => x.Attachments);

            if (lastMessageId.HasValue && !String.IsNullOrEmpty(order))
                query = order == "DESC" ? query.Where(x => x.Id > lastMessageId.Value) : query.Where(x => x.Id < lastMessageId.Value);

            if (count.HasValue)
                query = query.Take(count.Value);

            return query.ToList();
        }