Hwot to Calculating The Sum of values from DataGridView

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();

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)  
    {          
       int count = 0;
        if(e.Row.RowType==DataControlRowType.DataRow)  
        {  
            int col1Value =   Convert.ToInt32(e.Row.Cells[1].Text); // for first column value
            int col2Value =   Convert.ToInt32(e.Row.Cells[2].Text); // for second column value
           count += col1Value + col2Value;
        }  
    label1.Text = count.ToString();
    } 

int cnt=0;
protected void dgv_OnItemDataBound(object sender, DataGridItemEventArgs e)
{
            if(e.Item.ItemType == Listitemtype.Item || e.Item.ItemType == Listitemtype.AlternateItem )
           {
                     cnt + = Convert.ToInt32(e.Item.Cells[2].Text);
           } 
          lblResult.Text=cnt.ToString();
}