GridView Footer Total is incorrect if GridView is sorted in ASP.Net

hi friends

I am pasting my code here I want to sum of total CountDevice  in footer of template

 int total = 0;
    protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    {
       
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            total += Convert.ToInt32(DataBinder.Eval(e.Row.DataItem, "CountDevice"));
        }
        if (e.Row.RowType == DataControlRowType.Footer)
        {
            Label lblamount = (Label)e.Row.FindControl("lblTotal");
            lblamount.Text = "total:" + total.ToString();
        }
    }

i  am use sorting on column CountDevice

when sorting this column show double column in footer

for Example total countdevice is 100

when sorting on column CountDevice  total show 200