NullReference Exception when changing the color of rows in DGV on form load

Question

On form load event when I load data in datagridview after that I call this function to change color of those rows in which the paid expense is Yes but it gives me nullreference exception on the line

PaidStatus = ExpensesDataGridView.Rows[i].Cells[4].Value.ToString();

public void ExpenseRowColor()
    {
        int i;
        string PaidStatus;

        for (i = 1; i <= ExpensesDataGridView.Rows.Count; i++)
        {
            PaidStatus = ExpensesDataGridView.Rows[i].Cells[4].Value.ToString();

            if (PaidStatus == "Yes")
            {
                ExpensesDataGridView.Rows[i].DefaultCellStyle.BackColor = Color.LightGreen;
            }
        }
    }

PaidStatus = ExpensesDataGridView.Rows[i].Cells[4].Value.ToString(); — Aizaz hussain, Aug 30 '17 at 19:48
Yes but which part of that statement? `Cells` or `Value`? It's gotta be one of those if it's getting to that line. Debug and figure out which of those is null. — GBreen12, Aug 30 '17 at 19:49

Afnan Makhdoom · Answer 1 · 2017-08-31T23:01:01.920

0

Cells start from a 0th index, meaning that the 4th cell would be at [3] index . In the same way, the row and column indices start from 0 as well but your loop starts from an int i = 1 so I suggest you change that as well to: for (i = 0; i < ExpensesDataGridView.Rows.Count; i++){}

Or use foreach :

 foreach (DataGridViewRow row in ExpensesDataGridView)
 { 
     //use row here
 }

edited Aug 31 '17 at 23:01

answered Aug 30 '17 at 20:09

Afnan Makhdoom

666
8
19

There are 5 cloumns in DGV so the index for the cell stays 4 – Aizaz hussain Aug 30 '17 at 20:15
Fix the loop as i told you to – Afnan Makhdoom Aug 31 '17 at 05:05
tried it but still problem exist – Aizaz hussain Aug 31 '17 at 20:11
use foreach (DataGridViewRow row in ExpensesDataGridView) { //use row here } – Afnan Makhdoom Aug 31 '17 at 22:58

NullReference Exception when changing the color of rows in DGV on form load

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