sum of datagridview values

Question

I have form with datagridview with columns id,name,mark .and a textbox total.Iwant to find the sum of the mark when we entered the values into the datagridview.

int sum=0;

private void dataGridView1_CellValueChanged(object sender, DataGridViewCellEventArgs e)

{

for (int i = 0; i < dataGridView1.Rows.Count - 1; i++)

{

sum += Convert.ToInt32(dataGridView1.Rows[i].Cells["mark"].Value.ToString());

textBox1.Text = Convert.ToString(sum);

}

but the "Object reference not set to an instance of an object" error occurs, plz help;

sathish kumar · Answer

i have also this problem. but i am resolve this problem like this coding now its working. you also try it. here 1 is column index. int sum = 0; for (int i = 0; i { if (dataGridView1.Rows[i].Cells[1].Value != null) { sum += Convert.ToInt32(dataGridView1.Rows[i].Cells[1].Value.ToString()); textBox2.Text = Convert.ToString(sum); } }

Sam Hobbs · Answer

First it is likely occuring for the last row in the DataGridView. The last row is the one for adding rows. So you need to add code to ignore a row if the row index equals the DataGridView's NewRowIndex Property. That will likely eliminate the error you are getting. You should use code such as what Mahesh suggests though. Another way to do what Mahesh is suggesting is to use the Int32TryParse Method. I don't understand why the result is put into textBox1.Text in the for loop. That will update the textbox for every row. I think it needs to be done once after the loop.

Mahesh Chand · Answer

You need to put a check that the cell has a value and it can be converted. This is the case when your cell is not valid or the value in the cell is not balid. OR mark column is there. Several possiblities. Try one at a time. If (dataGridView1.Rows[i].Cells[mark].Value != null) { sum += Convert.ToInt32(dataGridView1.Rows[i].Cells[mark].Value.ToString()); textBox1.Text = Convert.ToString(sum); }