public IEnumerable <ShoppingCartDetailDto> GetItemsByCartIds(int[] cartIdArr)
 {
     if (cartIdArr.Length == 0)
     {
         return(null);
     }
     using (var cxt = DbContext(DbOperation.Read))
     {
         var repo = new ShoppingCartRepo(cxt);
         return(repo.GetItemsByCartIds(cartIdArr));
     }
 }