protected void btDelete_Click(object sender, EventArgs e)
 {
     try
     {
         foreach (GridViewRow row in dgvApprover.Rows)
         {
             CheckBox chk = (CheckBox)row.FindControl("cbChoose");
             if (chk.Checked)
             {
                 string sID = row.Cells[0].Text.Trim();
                 if (!sID.Equals(""))
                 {
                     int ID = Int32.Parse(sID);
                     um.deleteCoQuanLuuTru(ID);
                 }
             }
         }
         Session[Su_CoQuanLuuTruLogic.SESSION_SEC_ID] = null;
         Response.Redirect("QLCoQuanLuuTru.aspx", false);
     }
     catch (Exception ex)
     {
         Logger.logmessage(classobject, "btDelete_Click", ex.Message + ex.StackTrace);  Response.Redirect("~/ThongBaoLoi.aspx", false);
     }
 }