How to loop through every row in a datagridview?

Question

I'm trying to make the "Current Count" column of my DataGridView only accept integers. I've had success when I use

int value;
string str = my_datagridview.Rows[1].Cells["Current Count"].Value.ToString();
if (int.TryParse(str, out value))

But I'm sure there must be a way where I don't have to write that code for every individual row. I've tried it with a for loop and it gives me a NullReferenceExeption.

Here's my code (including NullReferenceException for loop):

//'Export data' button
    void export_button_Click(object sender, EventArgs e)
    {
        for (int i = 0; i < my_datagridview.RowCount; i++)
        {

        int value;
        string str = my_datagridview.Rows[i].Cells["Current Count"].Value.ToString();
        if (int.TryParse(str, out value))
        {
            //clears form and ensures new file will have header
            text_box_export.Text = "Item Code,Item Description,Current Count,On Order\r\n";

            //ints for for loops
            int row_count = my_datagridview.RowCount;
            int cell_count = my_datagridview.Rows[0].Cells.Count;

            //captures data for each row
            for (int row_index = 0; row_index <= row_count - 2; row_index++)
            {
                //captures data for each column in each row
                for (int cell_index = 0; cell_index < cell_count; cell_index++)
                {
                    //adds data to messagebox in stocklist format & leaves comma off the end of each line
                    if (cell_index <= 2)
                    {
                        text_box_export.Text = text_box_export.Text + my_datagridview.Rows[row_index].Cells[cell_index].Value.ToString() + ",";
                    }
                    else
                    {
                        text_box_export.Text = text_box_export.Text + my_datagridview.Rows[row_index].Cells[cell_index].Value.ToString();
                    }
                }
                text_box_export.Text = text_box_export.Text + "\r\n";
            }
            //writes new data from messagebox over stocklist.csv file
            System.IO.File.WriteAllText("c:\\Stockfile\\stocklist.csv", text_box_export.Text);
        }
        else
        {
            MessageBox.Show("Data not saved. Please enter only integers");
        }
    }
}

at which line NullReference exception is raised ? – tchelidze Jan 10 '16 at 07:14 — tchelidze, Jan 10 '16 at 07:14

tchelidze · Answer 1 · 2016-01-10T07:29:14.667

If your primary goal is to

to make the "Current Count" column of my DataGridView only accept integers

you can handle dataGridView1.EditingControl.KeyPress event and validate input in EventHandler method.
Try following

private string patternToMatchIntegerValues = @"^\d*$";

private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
{
  my_datagridview.EditingControl.KeyPress -= EditingControl_KeyPress;
  my_datagridview.EditingControl.KeyPress += EditingControl_KeyPress;
}

private void EditingControl_KeyPress(object sender, KeyPressEventArgs e)
{
  if (!char.IsControl(e.KeyChar))
  {
    var editingControl = (Control)sender;

    if (!Regex.IsMatch(editingControl.Text + e.KeyChar, patternToMatchIntegerValues))
      // Stop the character from being entered into the control since it is non-numerical.
      e.Handled = true;
  }
}

How to loop through every row in a datagridview?

1 Answers1