System.NullReferenceException:

[H Martins]

Hi. (I am Portuguese) ********UPDATE******* Looks like I found the problem In the first for() there was a 1 instead of an i. I realized that after increasing zoom level. I apologize. ************** I am a new-by to Visual Studio and C# classes and I am trying to extract a GridView content to a CSV format file. Handling and processing fields seems not too difficult but the extraction is fighting me. I run the compiler, the form shows up, I fill the grid clicking the fill button, it fills OK but when I press the button to export, I get: System.NullReferenceException: 'Object reference not set to an instance of an object.' System.Windows.Forms.DataGridViewCell.Value.get returned null. In both similar lines: writer.Write(dataGridViewMotor1.Rows[i].Cells[j].Value.ToString());

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.IO;

namespace Stepping
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

    private void dataGridView1\_CellContentClick(object sender, DataGridViewCellEventArgs e)
    {

    }

    private void btnSave01\_MouseClick(object sender, MouseEventArgs e)
    {
        TextWriter writer = new StreamWriter(@"H:\\proj\\\_Programacao\\\_Arduino\\ArduinoHM\\Stepper\_Polling\_us\\WinApp\\M01.txt");
        
        for (int i = 0; 1 < dataGridViewMotor1.Rows.Count - 1; i++)
        {
            for (int j = 0; j < dataGridViewMotor1.Columns.Count; j++)
            {
                if (j == 0)
                {
                    writer.Write(dataGridViewMotor1.Rows\[i\].Cells\[j\].Value.ToString());  
                }
                else
                {
                    writer.Write("," + dataGridViewMotor1.Rows\[i\].Cells\[j\].Value.ToString());
                }
            }
        }
        writer.Close();
        MessageBox.Show("Data Exported");
    }

    private void btnFillTestData\_MouseClick(object sender, MouseEventArgs e)
    {
        // Line, Abs, Rel, X, C\_t, C\_i, C\_n, MinSpeed, MaxSpeed, Accel, Decel
        dataGridViewMotor1.Rows.Add(1,0, 120,0,0,0,0, 10, 100, 0.9, 0.9 );
        dataGridViewMotor1.Rows.Add(2,0,12

[Lost User]

        for (int i = 0; 1 < dataGridViewMotor1.Rows.Count - 1; i++)

Your compare expression is still wrong. The expression 1 < dataGridViewMotor1.Rows.Count - 1 will always be true. It should be **i** < dataGridViewMotor1.Rows.Count. And a suggestion: don't rely on videos to teach you how to program. Get a good online tutorial, or book, and learn the actual language first. Using Windows forms and complex controls without understanding the structure of the language properly is a waste of your time.

[Richard Deeming]

Unless the Rows collection contains a blank insertion row at the end, in which case i < dgv.Rows.Count - 1 would be correct. :)

---

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

[Lost User]

Quite right. But any program worth its salt would be validating the content as it goes through them. And if there is not a blank row at the end then a complete line of data will be missed.