row data bound event in gridview

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C#

i am using the row data bound event in gridview. i have four records in gridview but when i am disply four records in label it display only first record four times. it does not execute the second and further records..
what is the problem ..

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            CheckBox chk = (CheckBox)e.Row.FindControl("CheckBox1");

            string s = "select id,title,user_id from document where category='" + drop_cat.SelectedItem.Value + "' and subctgry='" + drop_sub_cat.SelectedItem.Value + "'";
            SqlDataAdapter ad = new SqlDataAdapter(s, c.getcon());
            DataSet ds = new DataSet();
            ad.Fill(ds);

            if (ds.Tables[0].Rows.Count != 0)
            {
                x+= ds.Tables[0].Rows[0][1].ToString();
            }
            Label82.Text = x;
        }
    }

so, in the label first record display four times.... it does not execute 2nd and other..
whenevr row bound it only execute first..