Or you can use like this. This may be faster.
int iFindNo = 14;
int j = dataGridView1.Rows.Count-1;
int iRowIndex = -1;
for (int i = 0; i < Convert.ToInt32(dataGridView1.Rows.Count/2) +1; i++)
{
if (Convert.ToInt32(dataGridView1.Rows[i].Cells[0].Value) == iFindNo)
{
iRowIndex = i;
break;
}
if (Convert.ToInt32(dataGridView1.Rows[j].Cells[0].Value) == iFindNo)
{
iRowIndex = j;
break;
}
j--;
}
if (iRowIndex != -1)
MessageBox.Show("Index is " + iRowIndex.ToString());
else
MessageBox.Show("Index not found." );