datagridview中特定一列的求和

我想求datagridview中一列数据的总和，我应该怎么编写这段代码呢？

double sum = 0;
for (int i = 0; i < dataGridView1.Rows.Count; i++)
{
sum += Convert.ToDouble(dataGridView1.Rows[i].Cells["列"].Value);

            }
            textBox5.Text = sum.ToString();

double sum=0;
for (int i = 0; i < dataGridView.Rows.Count; i++)
{
sum += Convert.ToDouble(dataGridView.Rows[i].Cells[某列].Value);
}
sum就是和