public Book SaveBook(RegBook book)
        {
            return(repo.Transaction(() =>
            {
                Category category = Category.FindById(repo, book.CategoryId);
                Format format = Format.FindById(repo, book.FormatId);

                Book entity = book.create();
                if (category != null && format != null)
                {
                    entity.Category = category;
                    entity.Format = format;
                    entity.Save(repo);
                    return entity;
                }
                return null;
            }));
        }
 public Book SaveBook([FromBody] RegBook book)
 {
     return(service.SaveBook(book));
 }