public BlogPost Build()
 {
     var post = new BlogPost
     {
         Id = _id,
         Title = _title,
         SubTitle = _subTitle,
         Text = _text,
         PublicationDate = _publicationDate,
         AuthorName = _authorName
     };
     if (_comments!= null)
         foreach (var comment in _comments)
         {
             post.AddCommant(comment);
         }
     return post;
 }