I am getting an error on DGV cell click events

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I have an error('Object reference not set to an instance of an object.) on DGV Cell click events. My DGV has Computed coloums, I know that is the reason for this error but I do not know how to fix it. Therefor I am writing here. FYI, this app is for my personal use and training.

What I have tried:

Private Sub DGV_Trans_CellClick(sender As Object, e As DataGridViewCellEventArgs) Handles DGV_Trans.CellClick

      If e.RowIndex >= 0 Then

               Dim row As DataGridViewRow
               row = Me.DGV_Trans.Rows(e.RowIndex)

           TransIDTextBox.Text = row.Cells(1).Value.ToString
               CheckBox1.Checked = row.Cells(2).Value
               SymbolTextBox.Text = row.Cells(3).Value.ToString
               QuantityTextBox.Text = row.Cells(4).Value.ToString
               PriceTextBox.Text = row.Cells(5).Value.ToString
               DTP1.Value = row.Cells(6).Value
               TxtFee.Text = row.Cells(7).Value.ToString
               TxtVat.Text = row.Cells(8).Value.ToString

       End If

   End Sub

Posted 16-May-20 4:00am

qulaitks

Updated 17-May-20 20:27pm

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Comments

[no name] 16-May-20 10:07am

Which Cell is the problem? And you are aware that also for Cells the index starts at zero and the max. index will be "No of Cells - 1"?

qulaitks 16-May-20 10:13am

The computed cell is cell(9), when I click the DGV the rows 1 to 8 values suppose to show in the related textboxs

[no name] 16-May-20 10:16am

And index is not the problem? I mean in case you have 10 Columns the range to address them is row.Cells(0) up to row.Cells(9)

qulaitks 16-May-20 10:20am

Cell(0) is holding the ID which is auto generated

F-ES Sitecore 16-May-20 10:34am

Doesn't vb have 1-based indexes?

[no name] 16-May-20 10:44am

No idea, I don't know VB. But if that's the case, then that e.RowIndex >= 0 would also be a problem?

Dave Kreskowiak 16-May-20 10:45am

Not VB.NET.

F-ES Sitecore 16-May-20 11:52am

I thought that was the case with vb.net too. You learn something new every day :)

Richard MacCutchan 16-May-20 10:58am

Use your debugger to find out which line the error occurs on. And from that you should be able to trace back to the null reference.

qulaitks 16-May-20 13:18pm

I have tried it and is not shown any code error. The error I am having is when i cell click the DGV , its something to do with null-able values.

Dave Kreskowiak 16-May-20 15:39pm

This is the easiest error to find with with debugger. Set a breakpoint on the first line in your event handler and start inspecting the contents of variables. Execute a line of code, then inspect variables again.

If something is null, you're going to have to figure out why.

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Maciej Los · Answer 1 · 2020-05-17T20:28:00

Please, read comments in code block:

VB.NET

'try to get current row
Dim row As DataGridViewRow = Me.DGV_Trans.CurrentRow 
If row is Nothing Then Return 'or Exit Sub
'further instructions here
TransIDTextBox.Text = row.Cells(1).Value.ToString() 'second column
CheckBox1.Checked = row.Cells(2).Value '3. column
SymbolTextBox.Text = row.Cells(3).Value.ToString() '4. column
QuantityTextBox.Text = row.Cells(4).Value.ToString()
PriceTextBox.Text = row.Cells(5).Value.ToString()
DTP1.Value = row.Cells(6).Value
TxtFee.Text = row.Cells(7).Value.ToString()
TxtVat.Text = row.Cells(8).Value.ToString() '9. column

As 0x01AA has already stated, column index starts with 0 (zero)! So, correct above code accordingly!
For further details, please see:
DataGridView.Columns Property (System.Windows.Forms) | Microsoft Docs[^]
How to: Return a Value from a Procedure - Visual Basic | Microsoft Docs[^]