GridView添加小计行

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    {
       
        if (e.Row.RowIndex >= 0)
        {
            sum += Convert.ToDouble(e.Row.Cells[6].Text);
        }
        else if (e.Row.RowType == DataControlRowType.Footer)
        {
            e.Row.Cells[5].Text = "总薪水为：";
            e.Row.Cells[6].Text = sum.ToString();
            e.Row.Cells[3].Text = "平均薪水为：";
            e.Row.Cells[4].Text = ((int)(sum / GridView1.Rows.Count)).ToString();
           
        }
    }
}