// iterate over parent rows

foreach ( DataRow parentRow in myTable.Rows ) {
   // get parent row
   Response.Write ( parentRow [ "parentFieldName" ] );

   // iterate over child rows
   foreach ( DataRow childRow in parentRow.GetChildRows ( "relationName" ) ) {
      // get child row
      Response.Write ( childRow [ "childFieldName" ] );
   }
}

' iterate over parent rows
Dim parentRow As DataRow
For Each parentRow In  myTable.Rows
   ' get parent row
   Response.Write ( parentRow ( "parentFieldName" ) )
   ' iterate over child rows
   Dim childRow As DataRow
   For Each childRow In parentRow.GetChildRows ( "relationName" )
      ' get child row
      Response.Write ( childRow ( "childFieldName" ) )
   Next childRow
Next parentRow

void getChildSource ( Object src, DataListItemEventArgs e ) {
   if ( e.Item.ItemType == ListItemType.Item || 
         e.Item.ItemType == ListItemType.AlternatingItem ) {
      DataGrid childGrid = ( DataGrid ) e.Item.FindControl ( "Products" );
      childGrid.DataSource = ( ( DataRowView ) e.Item.DataItem ).CreateChildView ( "categoryId" );
      childGrid.DataBind ( );
   }
}

Sub getChildSource ( src As Object, e As DataListItemEventArgs )
   If e.Item.ItemType = ListItemType.Item Or _
         e.Item.ItemType = ListItemType.AlternatingItem Then
      Dim childGrid As DataGrid = CType ( e.Item.FindControl ( "Products" ), DataGrid )
      childGrid.DataSource = CType ( e.Item.DataItem, DataRowView ).CreateChildView ( "categoryId" )
      childGrid.DataBind ( )
   End If
End Sub