private void GetParentKeyConstraint ( ) {
   // get a DataRelation from a DataSet.
   DataRelation dr = myDataSet.Relations [ "CustomerOrders" ];
   // get the relation's parent key constraint.
   UniqueConstraint pkCstrt = dr.ParentKeyConstraint;
   // get the constraint's DataColumns
   DataColumn [ ] cstrtCols = pkCstrt.Columns;
   // print the column names.
   int i;
   for ( i = 0; i < cstrtCols.Length; i++ ) {
      Response.Write ( cstrtCols [ ].ColumnName );
   }
}

Private Sub GetParentKeyConstraint ( )
   ' get a DataRelation from a DataSet.
   Dim dr As DataRelation = myDataSet.Relations ( "CustomerOrders" )
   ' get the relation's parent key constraint.
   Dim pkCstrt As UniqueConstraint = dr.ParentKeyConstraint
   ' get the constraint's DataColumns
   Dim cstrtCols ( ) As DataColumn = pkCstrt.Columns
   ' print the column names.
   Dim i As Integer
   For i = 0 to cstrtCols.GetUpperBound ( 0 )
      Response.Write ( cstrtCols ( i ).ColumnName )
   Next i
End Sub