int sum = 0;
for (int i = 0; i < dataGridView1.Rows.Count; ++i)
{
sum += Convert.ToInt32(dataGridView1.Rows[i].Cells[1].Value);
}
label1.Text = sum.ToString();
int sum = 0;
for (int i = 0; i < dataGridView1.Rows.Count; ++i)
{
sum += Convert.ToInt32(dataGridView1.Rows[i].Cells[1].Value);
}
label1.Text = sum.ToString();