HOW TO CALCULATE COLUMN TOTAL IN DATAGRIDVIEW USING C#

// POPULATE THE DATAGRIDVIEW AND THEN INCLUDE THE FOLLOWING CODE IN ANY EVENT.HERE I AM USING IT IN A BUTTON CLICK EVENT.

private void button1_Click(object sender, EventArgs e)
{

int Total = 0;

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

{

Total += Convert.ToInt32(dataGridView1.Rows[i].Cells["Columnname"].Value);

}

textBox1.Text = Total.ToString();
}