public void deleteCategory(int id)
        {
            DanhMucSach e = db.DanhMucSaches.SingleOrDefault(x => x.MaDanhMuc == id);

            db.DanhMucSaches.Remove(e);
            db.SaveChanges();
        }
 public void createCategory(DanhMucSach e)
 {
     db.DanhMucSaches.Add(e);
     db.SaveChanges();
 }