ds.Tables.Add(dt);
        ds.Tables.Add(dt_dtl);
        CreateRelation(dt.Columns["id"], dt_dtl.Columns["id"], ds);

        // 创建关联
        private void CreateRelation(DataColumn masterCol, DataColumn detailCol, DataSet ds)
        {
            DataRelation relCustOrder;
            relCustOrder = new DataRelation("CustomersOrders ", masterCol, detailCol);
            ds.Relations.Add(relCustOrder);
        }