public async Task <IListResult <AuthorDto> > GetAllAuthor()
        {
            var result = await _authorRepository.GetAllListAsync();

            var list = new HashSet <AuthorDto>();

            foreach (var item in result)
            {
                list.AddIfNotContains(AuthorDto.MaptoDto(item));
            }

            return(new ListResultDto <AuthorDto>(list.ToList()));
        }