Solved

"System.NullReferenceException was unhandled" error after last valid row.

Posted on 2016-08-19
10
38 Views
Last Modified: 2016-08-19
Hi, I'm using Visual Studio 2010 C#. I have a DataGridView on one of my Forms that is connected to SQL database table. That part works. I'm also using the dataGridView1_RowEnter Event to populate the selected information into different Textboxes as I scroll down the grid. That works until I get past the last row.

As soon as I go beyond the length of the table (past the last row) and enter the first NULL row, I get the following error.  

ERROR: >> System.NullReferenceException was unhandled

Why is the  "if (e.RowIndex >= 0)" logic statement not preventing the error and how do I solve this problem?

private void dataGridView1_RowEnter(object sender, DataGridViewCellEventArgs e)
        {
            DataGridViewRow row = this.dataGridView1.Rows[e.RowIndex];
            if (e.RowIndex >= 0)
            {                
                textBox1.Text = row.Cells[1].Value.ToString();
                textBox2.Text = row.Cells[2].Value.ToString();
                textBox3.Text = row.Cells[3].Value.ToString();
                textBox4.Text = row.Cells[4].Value.ToString();
            }

Open in new window

0
Comment
Question by:Mr_Fulano
  • 4
  • 3
  • 3
10 Comments
 
LVL 44

Expert Comment

by:AndyAinscow
ID: 41762930
>>Why is the  "if (e.RowIndex >= 0)" logic statement not preventing the error and how do I solve this problem?

What is the value of e.RowIndex when it fails.  You are apparently assuming it is less than zero.
0
 
LVL 44

Accepted Solution

by:
AndyAinscow earned 500 total points
ID: 41762934
I suspect you want something like:

if (!row.IsNewRow)   //if (e.RowIndex >= 0)


https://msdn.microsoft.com/en-us/library/system.windows.forms.datagridviewrow.isnewrow(v=vs.110).aspx
0
 
LVL 62

Expert Comment

by:Fernando Soto
ID: 41762939
This statement needs to be in the if statement, first statement inside if statement.

 DataGridViewRow row = this.dataGridView1.Rows[e.RowIndex];
0
Efficient way to get backups off site to Azure

This user guide provides instructions on how to deploy and configure both a StoneFly Scale Out NAS Enterprise Cloud Drive virtual machine and Veeam Cloud Connect in the Microsoft Azure Cloud.

 
LVL 44

Expert Comment

by:AndyAinscow
ID: 41762962
@Fernando  
Why does that assignment need to be inside the if block?
0
 

Author Comment

by:Mr_Fulano
ID: 41763034
Hi Fernando, I had it that way and retried your suggestion just to make sure, but that still fails.
0
 

Author Comment

by:Mr_Fulano
ID: 41763036
Hi Andy, yes...your suggestion works. The last row is negative and keeps increasing each time I enter it (i.e. -1. -2. -3...etc).

Is there a way to not show that last row at all?
0
 
LVL 62

Expert Comment

by:Fernando Soto
ID: 41763052
Hi Andy, I was thinking that if this was happening when he passed the last row it had a -1 as the index and therefore would be an out of bounds index or no row. Was not near a computer to test and wanted him to have something to test for the moment.
0
 

Author Comment

by:Mr_Fulano
ID: 41763055
Thank you both...!!!
0
 
LVL 44

Expert Comment

by:AndyAinscow
ID: 41763059
Hi Fernando, I could understand why you suggested that for some of the other possible events but was puzzled why for the RowEnter event.  Thanks for clarifying.
0
 
LVL 62

Expert Comment

by:Fernando Soto
ID: 41763065
Not a problem Andy, have a great day.
0

Featured Post

PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Performance in games development is paramount: every microsecond counts to be able to do everything in less than 33ms (aiming at 16ms). C# foreach statement is one of the worst performance killers, and here I explain why.
The article shows the basic steps of integrating an HTML theme template into an ASP.NET MVC project
Although Jacob Bernoulli (1654-1705) has been credited as the creator of "Binomial Distribution Table", Gottfried Leibniz (1646-1716) did his dissertation on the subject in 1666; Leibniz you may recall is the co-inventor of "Calculus" and beat Isaac…
A short tutorial showing how to set up an email signature in Outlook on the Web (previously known as OWA). For free email signatures designs, visit https://www.mail-signatures.com/articles/signature-templates/?sts=6651 If you want to manage em…

770 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question