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I'm getting this error and I don't know how to fix it. I know i'm supposed to write what I've tried, but i have no idea what to try, even after looking for a few hours about how to deal with the error.

If more information is needed please let me know. Thanks

The highlighted part of the code is:

Dim cdtrabajador As String = dgvr.Cells(0).Value.ToString

Object reference not set to an instance of an object.

NullReference Exception was unhandled by user code

Private Sub PeopleDataGridView_CellFormatting(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellFormattingEventArgs) Handles DataGridView1.CellFormatting
    If DataGridView1.RowCount > 0 AndAlso e.RowIndex > -1 Then
        If e.RowIndex > -1 Then
            Dim dgvr As DataGridViewRow = DataGridView1.Rows(e.RowIndex)
            Dim cdtrabajador As String = dgvr.Cells(0).Value.ToString
            Dim qry = From dr As PersonalObraDataSet.PersonalObRow In PersonalObraDataSet.PersonalOb Where dr.cdTrabajador = cdtrabajador
            If qry.Count > 0 Then
                Dim Nombre As String = qry.First.Nombre1
                dgvr.Cells(1).Value = Nombre
            End If
        End If
    End If
End Sub
David
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    Just handle the case where your cell value is null (If you invoke `ToString` on null you get the error in question) – Kevin DiTraglia Jul 18 '13 at 16:20
  • doesn't visual basic use base 1 indices? Like dgvr.Cells(1) being the first cell? – Ted Jul 18 '13 at 16:21
  • I'm completely new to codding and i have no idea how to handle it, not even after looking examples, that is why i'm hopping someone can help with it. – David Jul 18 '13 at 16:22
  • Visual Basic uses base of 1. VB.Net uses base of 0. That much I know from my reading. – David Jul 18 '13 at 16:24
  • @David You are correct :-) – Chris Jul 18 '13 at 16:27
  • @David are you saying i.e. VB6 uses base 1? In what context? I remember using base 0. I think there is an `Option Base {0 | 1}` in VB6. The problem was that *some* controls used 0 and some used 1. – djv Jul 18 '13 at 20:00

1 Answers1

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Hard to say for sure what the root of the issue is, but you may be safe to just null check the cell before you attempt to perform any action on it, and return in the case where the cell is null. Something like:

Dim cellObj as Object = dgvr.Cells(0).Value
if Not cellObj = Nothing Then
      Dim cdtrabajador As String = cellObj.ToString
     '...
     'Perform the rest of your code
Else
     Return

Also note that if Cells(0) is actually null, invoking Value on it may also be causing the error. If you use your debugger you should be able to pinpoint which value is null and either handle it, or look into reasons why it is null if you expect a value to be present and it isn't.

Kevin DiTraglia
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  • `cellObj` is a temp variable used for convenience and isn't in your code because Kevin defined it in his example. – Michael Jul 18 '13 at 18:01
  • It IMPORTANT to remember not to check for IsNot Nothing on the Object, and NOT on a atribute. – JanBorup Jan 22 '14 at 22:36