how to delete rows using data relation in asp.net

DataColumn parentColumn =
           DataSet1.Tables["person"].Columns["sno"];
        DataColumn childColumn =
           DataSet1.Tables["dept"].Columns["no"];
        // Create DataRelation.
        DataRelation relCustOrder;
        relCustOrder = new DataRelation("CustomersOrders",
            parentColumn, childColumn);
        // Add the relation to the DataSet.
        DataSet1.Relations.Add(relCustOrder);
        //DataSet1.Relations.Add(relCustOrder);
        ForeignKeyConstraint fkeyConstraint = new ForeignKeyConstraint("fkey", parentColumn, childColumn);
        fkeyConstraint.DeleteRule = Rule.SetNull;