Sum of a column in gridview with paging and filtering.

decimal total = 0;
protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        total += Convert.ToDecimal(DataBinder.Eval(e.Row.DataItem, "calc"));
    }
    lblTotal.Text = total.ToString();
}