ช่วยด้วยครับ เรื่องเกี่ยวกับ Table asp มัน error ตรงที่ขีดเส้นใต้อ่ะครับ

 <asp:Table runat="server" ID="Table3" BorderColor="Black" BorderWidth="1">
</asp:Table>

protected void Page_Load(object sender, EventArgs e)
 {
if (!IsPostBack)
            {
                clsdb db = new clsdb(Convert.ToString(Session["sql"]));
                OleDbConnection dbcon;
                dbcon = db.connectdb();
                dbcon.Open();
                String sql = "select username from account";
                OleDbDataAdapter da;
                System.Data.DataSet dset = new System.Data.DataSet();
                System.Data.DataTable dt,dtng;
                da = new System.Data.OleDb.OleDbDataAdapter(sql, dbcon);
                da.Fill(dset);
                dt = dset.Tables[0];
                loadddl_line();
                Label1.Text = (String)dt.Rows[0]["username"];

                dtng = new System.Data.DataTable();
                dtng.Columns.Add("no");
                dtng.Columns.Add("part_no");
                dtng.Columns.Add("part_name");
                dtng.Columns.Add("qty");
                dtng.Columns.Add("cause");
                dtng.Columns.Add("remark");
                dtng.Columns.Add("actor");
                dtng.Columns.Add("cost");

                Session["dtng"] = dtng;

                bindata();
                genheadtable();
                genaddtable();
                loadddl_case();
                loaddl_actor();
            }
        }
 protected void genheadtable()
    {
        //--create row table
        TableRow tbrowh = new TableRow();
        tbrowh.ID = "r_h";
        tbrowh.Font.Bold = true;
        Table3.Rows.Add(tbrowh);

        //--create cell header part no
        TableCell tbcellpn = new TableCell();
        tbcellpn.ID = "h_pn";
        tbcellpn.Text = "Part No.";
        tbcellpn.BackColor = System.Drawing.Color.FromName("#CCFF99");
        tbcellpn.HorizontalAlign = HorizontalAlign.Center;
        tbrowh.Cells.Add(tbcellpn);
        //--create cell header part name
        TableCell tbcellpna = new TableCell();
        tbcellpna.ID = "h_pna";
        tbcellpna.Text = "Part Name";
        tbcellpna.BackColor = System.Drawing.Color.FromName("#CCFF99");
        tbcellpna.HorizontalAlign = HorizontalAlign.Center;
        tbrowh.Cells.Add(tbcellpna);
        //--create cell header qty
        TableCell tbcellqty = new TableCell();
        tbcellqty.ID = "h_qty";
        tbcellqty.Text = "Q'Ty";
        tbcellqty.BackColor = System.Drawing.Color.FromName("#CCFF99");
        tbcellqty.HorizontalAlign = HorizontalAlign.Center;
        tbrowh.Cells.Add(tbcellqty);
        //--create cell header unit
        TableCell tbcellu = new TableCell();
        tbcellu.ID = "h_unit";
        tbcellu.Text = "Unit";
        tbcellu.BackColor = System.Drawing.Color.FromName("#CCFF99");
        tbcellu.HorizontalAlign = HorizontalAlign.Center;
        tbrowh.Cells.Add(tbcellu);
        //--Create cell header cause
        TableCell tbcellca = new TableCell();
        tbcellca.ID = "h_ca";
        tbcellca.Text = "Cause";
        tbcellca.BackColor = System.Drawing.Color.FromName("#CCFF99");
        tbcellca.HorizontalAlign = HorizontalAlign.Center;
        tbrowh.Cells.Add(tbcellca);
        //--Create cell header remark
        TableCell tbcellrm = new TableCell();
        tbcellrm.ID = "h_rm";
        tbcellrm.Text = "Remark";
        tbcellrm.BackColor = System.Drawing.Color.FromName("#CCFF99");
        tbcellrm.HorizontalAlign = HorizontalAlign.Center;
        tbrowh.Cells.Add(tbcellrm);
        //--Create cell header actor
        TableCell tbcellact = new TableCell();
        tbcellact.ID = "h_act";
        tbcellact.Text = "Actor";
        tbcellact.BackColor = System.Drawing.Color.FromName("#CCFF99");
        tbcellact.HorizontalAlign = HorizontalAlign.Center;
        tbrowh.Cells.Add(tbcellact);
        //--create cell header vender
        TableCell tbcellven = new TableCell();
        tbcellven.ID = "h_ven";
        tbcellven.Text = "Vender";
        tbcellven.BackColor = System.Drawing.Color.FromName("#CCFF99");
        tbcellven.HorizontalAlign = HorizontalAlign.Center;
        tbrowh.Cells.Add(tbcellven);
        //--create cell header location
        TableCell tbcelllc = new TableCell();
        tbcelllc.ID = "h_lc";
        tbcelllc.Text = "L/C";
        tbcelllc.BackColor = System.Drawing.Color.FromName("#CCFF99");
        tbcelllc.HorizontalAlign = HorizontalAlign.Center;
        tbrowh.Cells.Add(tbcelllc);
        //--create cell header cost
        TableCell tbcellcos = new TableCell();
        tbcellcos.ID = "h_cost";
        tbcellcos.Text = "Cost";
        tbcellcos.BackColor = System.Drawing.Color.FromName("#CCFF99");
        tbcellcos.HorizontalAlign = HorizontalAlign.Center;
        tbrowh.Cells.Add(tbcellcos);
        //--create cell header add cause 
        TableCell tbcellac = new TableCell();
        tbcellac.ID = "h_ac";
        tbcellac.Text = "Add Cause";
        tbcellac.BackColor = System.Drawing.Color.FromName("#CCFF99");
        tbcellac.HorizontalAlign = HorizontalAlign.Center;
        tbrowh.Cells.Add(tbcellac);
        //--create cell header del cause
        TableCell tbcelldc = new TableCell();
        tbcelldc.ID = "h_dc";
        tbcelldc.Text = "Del Cause";
        tbcelldc.BackColor = System.Drawing.Color.FromName("#CCFF99");
        tbcelldc.HorizontalAlign = HorizontalAlign.Center;
        tbrowh.Cells.Add(tbcelldc);
        //--create cell header add list
        TableCell tbcellal = new TableCell();
        tbcellal.ID = "h_al";
        tbcellal.Text = "ADD List";
        tbcellal.BackColor = System.Drawing.Color.FromName("#CCFF99");
        tbcellal.HorizontalAlign = HorizontalAlign.Center;
        tbrowh.Cells.Add(tbcellal);
    }

    protected void genaddtable()
    {
        //--create row table
        TableRow tbrowadd = new TableRow();
        tbrowadd.ID = "r_add";
        tbrowadd.Font.Bold = true;
        Table3.Rows.Add(tbrowadd);

        //--create cell add part no
        DropDownList ddl_part = new DropDownList();
        ddl_part.ID = "ddl_part";
        ddl_part.AutoPostBack = true;
        ddl_part.AppendDataBoundItems = true;
        TableCell tbcellapn = new TableCell();
        tbcellapn.ID = "addpn";
        tbcellapn.Controls.Add(ddl_part);
        tbrowadd.Cells.Add(tbcellapn);

        //--create cell add part name
        TextBox tb_partname = new TextBox();
        tb_partname.ID = "tb_partname";
        tb_partname.ReadOnly = true;
        tb_partname.Width = 200;
        TableCell tbcellapna = new TableCell();
        tbcellapna.ID = "addpna";
        tbcellapna.Controls.Add(tb_partname);
        tbrowadd.Cells.Add(tbcellapna);

        //--create cell add qty
        TextBox tb_qty = new TextBox();
        tb_qty.ID = "tb_qty";
        tb_qty.Width = 50;
        TableCell tbcellaq = new TableCell();
        tbcellaq.ID = "addqty";
        tbcellaq.Controls.Add(tb_qty);
        tbrowadd.Cells.Add(tbcellaq);

        //--create cell add unit
        TextBox tb_unit = new TextBox();
        tb_unit.ID = "tb_unit";
        tb_unit.Width = 30;
        tb_unit.ReadOnly = true;
        TableCell tbcellau = new TableCell();
        tbcellau.ID = "addunit";
        tbcellau.Controls.Add(tb_unit);
        tbrowadd.Cells.Add(tbcellau);

        //--create cell add cause
        DropDownList ddl_cause = new DropDownList();
        ddl_cause.ID = "ddl_cause";
        ddl_cause.SelectedIndex = 0;
        ddl_cause.AppendDataBoundItems = true;
        TableCell tbcellacause = new TableCell();
        tbcellacause.ID = "addcause";
        tbcellacause.Controls.Add(ddl_cause);
        tbrowadd.Cells.Add(tbcellacause);

        //--create cell add remark
        TextBox tb_remark = new TextBox();
        tb_remark.ID = "tb_remark";
        tb_remark.TextMode = TextBoxMode.MultiLine;
        TableCell tbcellar = new TableCell();
        tbcellar.ID = "addremark";
        tbcellar.Controls.Add(tb_remark);
        tbrowadd.Cells.Add(tbcellar);

        //--create cell add actor
        DropDownList ddl_actor = new DropDownList();
        ddl_actor.ID = "ddl_actor";
        ddl_actor.SelectedIndex = 0;
        ddl_actor.AppendDataBoundItems = true;
        TableCell tbcellaact = new TableCell();
        tbcellaact.ID = "addactor";
        tbcellaact.Controls.Add(ddl_actor);
        tbrowadd.Cells.Add(tbcellaact);

        //--create cell add vender
        TextBox tb_ven = new TextBox();
        tb_ven.ID = "tb_ven";
        tb_ven.ReadOnly = true;
        TableCell tbcellav = new TableCell();
        tbcellav.ID = "addvender";
        tbcellav.Controls.Add(tb_ven);
        tbrowadd.Cells.Add(tbcellav);

        //--create cell add L/C
        TextBox tb_lc = new TextBox();
        tb_lc.ID = "tb_lc";
        tb_lc.ReadOnly = true;
        tb_lc.Width = 30;
        TableCell tbcellalc = new TableCell();
        tbcellalc.ID = "addlc";
        tbcellalc.Controls.Add(tb_lc);
        tbrowadd.Cells.Add(tbcellalc);

        //--create add cost
        TextBox tb_cost = new TextBox();
        tb_cost.ID = "tb_cost";
        tb_cost.Width = 50;
        TableCell tbcellacos = new TableCell();
        tbcellacos.ID = "addcost";
        tbcellacos.Controls.Add(tb_cost);
        tbrowadd.Cells.Add(tbcellacos);

        //--create add button add cause
        Button add_cause = new Button();
        add_cause.ID = "bt_addc";
        add_cause.Text = "ADD Cause";
        TableCell tbcelladdc = new TableCell();
        tbcelladdc.ID = "addc";
        tbcelladdc.Controls.Add(add_cause);
        tbrowadd.Cells.Add(tbcelladdc);

        //--create add button del cause
        Button del_cause = new Button();
        del_cause.ID = "bt_delc";
        del_cause.Text = "DEL Cause";
        TableCell tbcelldelc = new TableCell();
        tbcelldelc.ID = "delc";
        tbcelldelc.Controls.Add(del_cause);
        tbrowadd.Cells.Add(tbcelldelc);

        //--create add button add list
        Button add_list = new Button();
        add_list.ID = "bt_addl";
        add_list.Text = "Add List";
        TableCell tbcellal = new TableCell();
        tbcellal.ID = "addl";
        tbcellal.Controls.Add(add_list);
        tbrowadd.Cells.Add(tbcellal);
    }

    protected void loadddl_line()
    {
        clsdb db = new clsdb(Convert.ToString(Session["sql"]));
        OleDbConnection dbcon;
        dbcon = db.connectdb();
        dbcon.Open();
        String sql = "select line_no from dt_line";
        OleDbDataAdapter da;
        System.Data.DataSet dset = new System.Data.DataSet();
        System.Data.DataTable dt;
        da = new System.Data.OleDb.OleDbDataAdapter(sql, dbcon);
        da.Fill(dset);
        dt = dset.Tables[0];

        this.ddl_line.Items.Add("Select Model");
        this.ddl_line.DataSource = dt;
        this.ddl_line.DataTextField = "line_no";
        this.ddl_line.DataBind();
        db.closedb();
    }

    protected void loadddl_case()
    {
        clsdb db = new clsdb(Convert.ToString(Session["sql"]));
        OleDbConnection dbcon;
        dbcon = db.connectdb();
        dbcon.Open();
        String sql = "select cause_name from dt_cause";
        OleDbDataAdapter da;
        System.Data.DataSet dset = new System.Data.DataSet();
        System.Data.DataTable dt;
        da = new System.Data.OleDb.OleDbDataAdapter(sql, dbcon);
        da.Fill(dset);
        dt = dset.Tables[0];
        ((DropDownList)Table3.Rows[1].Cells[4].FindControl("ddl_cause")).DataSource = dt;
        ((DropDownList)Table3.Rows[1].Cells[4].FindControl("ddl_cause")).DataTextField = "cause_name";
        ((DropDownList)Table3.Rows[1].Cells[4].FindControl("ddl_cause")).DataBind();
        db.closedb();
    }

    protected void loaddl_actor()
    {
        clsdb db = new clsdb(Convert.ToString(Session["sql"]));
        OleDbConnection dbcon;
        dbcon = db.connectdb();
        dbcon.Open();
        String sql = "select actor_name from dt_actor";
        OleDbDataAdapter da;
        System.Data.DataSet dset = new System.Data.DataSet();
        System.Data.DataTable dt;
        da = new System.Data.OleDb.OleDbDataAdapter(sql, dbcon);
        da.Fill(dset);
        dt = dset.Tables[0];
        ((DropDownList)Table3.Rows[1].Cells[6].FindControl("ddl_actor")).DataSource = dt;
        ((DropDownList)Table3.Rows[1].Cells[6].FindControl("ddl_actor")).DataTextField = "actor_name";
        ((DropDownList)Table3.Rows[1].Cells[6].FindControl("ddl_actor")).DataBind();
        db.closedb();
    }

    protected void ddl_line_sic(Object sender, EventArgs e)
    {
        clsdb db = new clsdb(Convert.ToString(Session["sql"]));
        OleDbConnection dbcon;
        dbcon = db.connectdb();
        dbcon.Open();

        Label2.Visible = true;
        L_linename.Visible = true;

        String sql = "select line_name from dt_line where line_no ='" + ddl_line.SelectedItem.Value + "'";
        System.Data.OleDb.OleDbDataAdapter da = new OleDbDataAdapter(sql, dbcon);
        System.Data.DataSet dset = new System.Data.DataSet();
        da.Fill(dset);
        L_linename.Text = "  " + (String)dset.Tables[0].Rows[0]["line_name"];

        da = null;
        dset = null;

        sql = "select * from dt_part where line_no = '" + ddl_line.SelectedItem.Value + "'";
        da = new OleDbDataAdapter();
        dset = new System.Data.DataSet();
        System.Data.DataTable dt;
        da = new System.Data.OleDb.OleDbDataAdapter(sql, dbcon);
        da.Fill(dset);
        dt = dset.Tables[0];

        while (((DropDownList)Table3.Rows[1].Cells[0].FindControl("ddl_part")).Items.Count != 0)
        {
            ((DropDownList)Table3.Rows[1].Cells[0].FindControl("ddl_part")).Items.RemoveAt(0);
        }
        ((DropDownList)Table3.Rows[1].Cells[0].FindControl("ddl_part")).Items.Add("Part NO.");
        ((DropDownList)Table3.Rows[1].Cells[0].FindControl("ddl_part")).DataSource = dt;
        ((DropDownList)Table3.Rows[1].Cells[0].FindControl("ddl_part")).DataTextField = "part_no";
        ((DropDownList)Table3.Rows[1].Cells[0].FindControl("ddl_part")).DataBind();

        da = null;
        dset = null;
        dt = null;

        da = new OleDbDataAdapter();
        dset = new System.Data.DataSet();
        dt = new System.Data.DataTable();
        if (((DropDownList)Table3.Rows[1].Cells[0].FindControl("ddl_part")).SelectedIndex == 0)
        { }
        else
        {
            sql = "select * from dt_part where part_no = '" + ((DropDownList)Table3.Rows[1].Cells[0].FindControl("ddl_part")).SelectedItem.Value + "'";
            da = new System.Data.OleDb.OleDbDataAdapter(sql, dbcon);
            da.Fill(dset);
            dt = dset.Tables[0];

            ((TextBox)Table3.Rows[1].Cells[1].FindControl("tb_partname")).Text = (String)dt.Rows[0]["part_name"];
            db.closedb();
        }
    }