private static void GetChildRowsFromDataRelation()    {        /* For each row in the table, get the child rows using the        ChildRelations. For each item in the array, print the value        of each column. */        DataTable table = CreateDataSet().Tables["Customers"];        DataRow[] childRows;        foreach(DataRelation relation in table.ChildRelations)        {            foreach(DataRow row in table.Rows)            {                PrintRowValues(new DataRow[] {row}, "Parent Row");                childRows = row.GetChildRows(relation);                // Print values of rows.                PrintRowValues(childRows, "child rows");            }        }    }    public static DataSet CreateDataSet()    {        // create a DataSet with one table, two columns        DataSet dataSet = new DataSet();        // create Customer table        DataTable table = new DataTable("Customers");        dataSet.Tables.Add(table);        table.Columns.Add("customerId", typeof(int)).AutoIncrement = true;        table.Columns.Add("name", typeof(string));        table.PrimaryKey = new DataColumn[] { table.Columns["customerId"] };        // create Orders table        table = new DataTable("Orders");        dataSet.Tables.Add(table);        table.Columns.Add("orderId", typeof(int)).AutoIncrement = true;        table.Columns.Add("customerId", typeof(int));        table.Columns.Add("amount", typeof(double));        table.PrimaryKey = new DataColumn[] { table.Columns["orderId"] };        // create relation        dataSet.Relations.Add(dataSet.Tables["Customers"].Columns["customerId"],            dataSet.Tables["Orders"].Columns["customerId"]);            // populate the tables         int orderId = 1;        for(int customerId=1; customerId<=10; customerId++)        {            // add customer record            dataSet.Tables["Customers"].Rows.Add(                new object[] { customerId,                 string.Format("customer{0}", customerId) });                    // add 5 order records for each customer             for(int i=1; i<=5; i++)            {                dataSet.Tables["Orders"].Rows.Add(                    new object[] { orderId++, customerId, orderId * 10 });            }        }        return dataSet;    }    private static void PrintRowValues(DataRow[] rows, string label)    {        Console.WriteLine("\n{0}", label);        if(rows.Length <= 0)        {            Console.WriteLine("no rows found");            return;        }        foreach(DataRow row in rows)        {            foreach(DataColumn column in row.Table.Columns)            {                Console.Write("\table {0}", row[column]);            }            Console.WriteLine();        }    }

private void CreateConstraint(DataSet dataSet,     string table1, string table2, string column1, string column2){    ForeignKeyConstraint idKeyRestraint = new         ForeignKeyConstraint(dataSet.Tables[table1].Columns[column1],        dataSet.Tables[table2].Columns[column2]);    // Set null values when a value is deleted.    idKeyRestraint.DeleteRule = Rule.SetNull;    idKeyRestraint.UpdateRule = Rule.Cascade;    // Set AcceptRejectRule to cascade changes.    idKeyRestraint.AcceptRejectRule = AcceptRejectRule.Cascade;    dataSet.Tables[table1].Constraints.Add(idKeyRestraint);    dataSet.EnforceConstraints = true;}