loop through grid

I'm getting an error msg on this line:

For Each dr In ds.Tables("cards").Rows

I have data in my grid, not sure why I'm getting this msg.

An unhandled exception of type 'System.NullReferenceException' occurred in pcms.exe

Additional information: Object reference not set to an instance of an object.

VB Code:

Dim cmdView As OleDb.OleDbDataAdapter = New OleDb.OleDbDataAdapter("select item_no, activity, account_no from pcms.pcms_item_activity where item_no='" & txtItem.Text & "' and activity='" & txtActivity.Text & "'", objCon)
        ds = New DataSet()
        cmdView.Fill(ds, "cards")
        DataGrid1.DataSource = ds
        DataGrid1.DataMember = "cards"
        objCon.Close()
 
 Dim dr As DataRow
        For Each dr In ds.Tables("cards").Rows
            MsgBox("Whatever")
        Next

Not sure why you're getting the error, but the first thing that comes to my mind is why do you need to look at the datarow like that. I'd just look through the rows.....

VB Code:

'Populate your DataSet using your own code, then ....
Dim iMaxRec As Integer = DS.Tables("cards").Rows.Count
If iMaxRec > 0 Then
    For iLpr As Integer = 0 To iMaxRec - 1
        msgbox "Sample: " & DS.Tables("cards").Rows(iLpr).Item("yourfieldnamehere") 
    Next iLpr
End If