private void CreateRelation() 
{
    // Get the DataColumn objects from two DataTable objects 
    // in a DataSet. Code to get the DataSet not shown here.
    DataColumn parentColumn = 
        DataSet1.Tables["Customers"].Columns["CustID"];
    DataColumn childColumn = 
        DataSet1.Tables["Orders"].Columns["CustID"];
    // Create DataRelation.
    DataRelation relCustOrder;
    relCustOrder = new DataRelation("CustomersOrders", 
        parentColumn, childColumn);
    // Add the relation to the DataSet.
    DataSet1.Relations.Add(relCustOrder);
}