<asp:Table ID="tblReport" runat="server" BorderStyle="Solid" GridLines="Both" HorizontalAlign="Right" BorderColor="#9999FF" Width="100%">
        <asp:TableHeaderRow runat="server" HorizontalAlign="Left" BackColor="LightSkyBlue" CssClass=table-header>
            <asp:TableHeaderCell>1</asp:TableHeaderCell>
            <asp:TableHeaderCell>2</asp:TableHeaderCell>
            <asp:TableHeaderCell>3</asp:TableHeaderCell>
            ......
            <asp:TableHeaderCell>25</asp:TableHeaderCell>
        </asp:TableHeaderRow>
    </asp:Table>

while(reader.Read())
            {
                TableRow row = new TableRow();
                
                // M_ID
                TableCell cell = new TableCell();
                cell.Style.Add("text-align","center");

                CheckBox cb = new CheckBox();

                cb.Attributes.Add("ID", reader["M_ID"].ToString());
                cb.CssClass = "phat-report-id";

                cell.Controls.Add(cb);
                row.Cells.Add(cell);


                cell = new TableCell();
                cell.Text = reader["Name"].ToString();
                row.Cells.Add(cell);

                row.Cells.Add(cell);

                tblReport.Rows.Add(row);
}

//we skip the first row because it header row
for (int i = 1; i < tblReport.Rows.Count; i++)
{
    CheckBox check_box = (CheckBox)tblReport.Rows[i].Cells[0].Controls[0];
   
   if (check_box.Checked)
   {
       checked_box++;
   }
}

protected void Page_Load(object sender, EventArgs e)
{
 if (!IsPostBack)
 {
     ....
 }
btnFilter_Click(sender, e);
}

protected void Page_Load(object sender, EventArgs e)
{
 if (!IsPostBack)
 {
    ....
   btnFilter_Click(sender, e);
 }

}

string user_identity_name = User.Identity.Name;
                string[] user_name = user_identity_name.Split('\\');
                string user_id = user_name[1];

                cmd.CommandText = string.Format("SELECT * FROM tblMaslul_User WHERE USER_ID = '{0}'", user_id);
                SqlDataReader reader = cmd.ExecuteReader();

                while (reader.Read())
                {
                    Session["userid"] = reader["USER_ID"].ToString();
                    Session["merhav_id"] = reader["PLANT_ID"].ToString(); 
                    Session["yaam_id"] = reader["LOCATION_ID"].ToString(); 
                    Session["ezor_id"] = reader["REGION_ID"].ToString();
                    Session["PHAT_APPR_LEVEL"] = reader["PHAT_APPR_LEVEL"].ToString(); // PHAT_APPR_LEVEL
                }
                reader.Close();