public async Task <ResponseMessage <(Guid bookId, Guid seriesId)> > AddBookToSeries(Guid bookId, Guid seriesId) { var response = new ResponseMessage <(Guid bookId, Guid seriesId)>(); if (!await _seriesRepository.CheckAvailabilityAddingBookToSeries(bookId, seriesId)) { response.RawData = $"Can't add book with id {bookId} to series with id {seriesId}."; return(response); } response.Payload = await _seriesRepository.AddBookToSeries(bookId, seriesId); return(response); }