public IEnumerable <Models.Comment> GetCommentsPage(long postId, int page, int onPage)
 {
     if (page > GetCommentsPageCount(postId, onPage))
     {
         return(null);
     }
     return(DbSet_
            .Where(x => x.PostId == postId)
            .OrderByDescending(x => x.PostingTime)
            .Skip(onPage * (page - 1)).Take(onPage)
            .ToList());
 }
        public int GetCommentsPageCount(long postId, int onPage)
        {
            int count = DbSet_.Where(x => x.PostId == postId).Count();

            return(count / onPage + (count % onPage == 0 ? 0 : 1));
        }