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Object reference not set to an Instance

Hello All,
Am getting the Object reference not set to an instance error message when I load my form contaning a datagridview whenever the grid has null values.

How do i resolve that?

I have put default fro null as 0 in the datagridview formating.

 Private Function TotalGrossWgt() As Double
        Dim tot As Double = 0
        Dim i As Integer = 0
        If Not GardenInvoiceDtlDataGridView Is Nothing And Not GardenInvoiceDtlDataGridView.CurrentRow.IsNewRow Then
            For i = 0 To GardenInvoiceDtlDataGridView.Rows.Count - 1
                tot = tot + Convert.ToDouble(GardenInvoiceDtlDataGridView.Rows(i).Cells("DataGridViewTextBoxColumn21").Value)
            Next i
        End If
        Return tot
    End Function
    Private Function TotalNetWgt() As Double
        Dim tot As Double = 0
        Dim i As Integer = 0
        If Not GardenInvoiceDtlDataGridView Is Nothing And Not GardenInvoiceDtlDataGridView.CurrentRow.IsNewRow Then
            For i = 0 To GardenInvoiceDtlDataGridView.Rows.Count - 1
                tot = tot + Convert.ToDouble(GardenInvoiceDtlDataGridView.Rows(i).Cells("DataGridViewTextBoxColumn20").Value)
            Next i
        End If
        Return tot
    End Function
    Private Function NetWgt() As Double
        Dim tot As Double = 0
        Dim i As Integer = 0
        If Not GardenInvoiceDtlDataGridView Is Nothing And Not GardenInvoiceDtlDataGridView.CurrentRow.IsNewRow Then
            For i = 0 To GardenInvoiceDtlDataGridView.Rows.Count - 1
                tot = tot + Convert.ToDouble(GardenInvoiceDtlDataGridView.Rows(i).Cells("DataGridViewTextBoxColumn19").Value)
            Next i
        End If
        Return tot
    End Function
    Private Function TotalQty() As Double
        Dim tot As Double = 0
        Dim i As Integer = 0
        If Not GardenInvoiceDtlDataGridView Is Nothing And Not GardenInvoiceDtlDataGridView.CurrentRow.IsNewRow Then
            For i = 0 To GardenInvoiceDtlDataGridView.Rows.Count - 1
                tot = tot + Convert.ToDouble(GardenInvoiceDtlDataGridView.Rows(i).Cells("DataGridViewTextBoxColumn18").Value)
            Next i
        End If
        Return tot
    End Function

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 Try
            TxtTotalQty.Text = 0
            TxtNetWgt.Text = 0
            TxtTotalNetWgt.Text = 0
            TxtGrossweight.Text = 0
            If Not (GardenInvoiceDtlDataGridView.CurrentRow.IsNewRow) And GardenInvoiceDtlDataGridView.Rows.Count > 0 Then
                TxtTotalQty.Text = TotalQty().ToString("N")
                TxtNetWgt.Text = NetWgt().ToString("N")
                TxtTotalNetWgt.Text = TotalNetWgt().ToString("N")
                TxtGrossweight.Text = TotalGrossWgt().ToString("N")
            End If
        Catch ex As Exception
            MessageBox.Show(ex.Message, "Tea Tracing| GridFooter Changing", MessageBoxButtons.OK, MessageBoxIcon.Error)
        End Try

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Meir Rivkin

which line throws the error?

Meir Rivkin

try debug your code and when reach the line that throws the exception, add a validation check to make sure that it's not null.

Chris Roth

Is it possible that GardenInvoiceDtlDataGridView.CurrentRow is nothing, even if GardenInvoiceDtlDataGridView is not Nothing?

Meir Rivkin

yes it is possible, u need to check if GardenInvoiceDtlDataGridView.CurrentRow is not null first.

Norman Maina

ASKER

Error is Thrown here:
If Not (GardenInvoiceDtlDataGridView.CurrentRow.IsNewRow) And GardenInvoiceDtlDataGridView.Rows.Count > 0 Then
....

sedgwick>let em check as per your suggestion -Thanls very much for the quick response.Will get back to you.

Norman Maina

ASKER

sedgwick>I tried

If not  GardenInvoiceDtlDataGridView.Currencell.value is nothing

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Not working

Meir Rivkin

try:

if GardenInvoiceDtlDataGridView.Currencell is not nothing then

Norman Maina

ASKER

I have put this code on the paint event of the datagridview -it works fine until if finds rows with no values thats when it brings teh object reference not set to an instance error.

Private Function TotalQty() As Double
        Dim tot As Double = 0
        Dim i As Integer = 0
        If Not GardenInvoiceDtlDataGridView Is Nothing And Not GardenInvoiceDtlDataGridView.CurrentRow.IsNewRow Then
            For i = 0 To GardenInvoiceDtlDataGridView.Rows.Count - 1
                tot = tot + Convert.ToDouble(GardenInvoiceDtlDataGridView.Rows(i).Cells("DataGridViewTextBoxColumn18").Value)
            Next i
        End If
        Return tot
    End Function

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Nasir Razzaq

>Not GardenInvoiceDtlDataGridView.CurrentRow.IsNewRow

That is the issue still. CurrentRow is null and you are trying to access it.

Why do you need to test that when you are just looping through all the rows?

If you do need that then use another if condition

If(Not IsNothing(GardenInvoiceDtlDataGridView.CurrentRow))

ASKER CERTIFIED SOLUTION

Meir Rivkin

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Meir Rivkin

you can also use foreach as well:

For Each row As var In GardenInvoiceDtlDataGridView.Rows.Cast(Of DataGridViewRow)()
	tot += row.Cells("DataGridViewTextBoxColumn18").Value
Next

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or linq:

tot = GardenInvoiceDtlDataGridView.Rows.Cast(Of DataGridViewRow)().Sum(Function(n) n.Cells("DataGridViewTextBoxColumn18").Value)

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Norman Maina

ASKER

Sorry for late response -it worked like a charm.

Imagine i had commented the exception message to hide the problem.Now my code is fine,thanks to you.