การใส่ค่าว่างของ integer ในฐานข้อมูล <font color=red>ช่วยดูโค้ดให้หน่อยนะค่ะ ต้องการส่งค่าว่างหรือ null ลงในฐานข้อมูล

 protected void Button3_Click(object sender, EventArgs e)
    {
        ListItemCollection listLine = new ListItemCollection();
        listLine.Add(new ListItem(DropDownList11.SelectedItem.Text, DropDownList11.SelectedValue));
        listLine.Add(new ListItem(DropDownList12.SelectedItem.Text, DropDownList12.SelectedValue));
        listLine.Add(new ListItem(DropDownList13.SelectedItem.Text, DropDownList13.SelectedValue));
        listLine.Add(new ListItem(DropDownList14.SelectedItem.Text, DropDownList14.SelectedValue));
        listLine.Add(new ListItem(DropDownList15.SelectedItem.Text, DropDownList15.SelectedValue));
        listLine.Add(new ListItem(DropDownList16.SelectedItem.Text, DropDownList16.SelectedValue));
        listLine.Add(new ListItem(DropDownList17.SelectedItem.Text, DropDownList17.SelectedValue));
        listLine.Add(new ListItem(DropDownList18.SelectedItem.Text, DropDownList18.SelectedValue));
        listLine.Add(new ListItem(DropDownList19.SelectedItem.Text, DropDownList19.SelectedValue));
        listLine.Add(new ListItem(DropDownList20.SelectedItem.Text, DropDownList20.SelectedValue));
        listLine.Add(new ListItem(DropDownList21.SelectedItem.Text, DropDownList21.SelectedValue));
        listLine.Add(new ListItem(DropDownList22.SelectedItem.Text, DropDownList22.SelectedValue));
        listLine.Add(new ListItem(DropDownList33.SelectedItem.Text, DropDownList33.SelectedValue));

        DataSet ds = new DataSet();
        DataTable dt = new DataTable();


        foreach (ListItem item in listLine)
        {
            dt.Columns.Add(item.Text);
        }

        ds.Tables.Add(dt);
        ds.AcceptChanges();

        GridView3.DataSource = listLine;
        GridView3.DataBind();


        //นำค่าจาก gridview เก็บในฐานข้อมูล
        SqlConnection myConn = new SqlConnection(WebConfigurationManager.ConnectionStrings["LocalSqlServer"].ConnectionString);

        if (myConn.State == ConnectionState.Closed)
            myConn.Open();
        string sql = "";
        SqlTransaction tr = myConn.BeginTransaction();
        SqlCommand cmd = myConn.CreateCommand();


        cmd.CommandType = CommandType.Text;
        cmd.Transaction = tr;

        int F01;
        int F02;
        int F03;
        int F04;
        int F05;
        int F06;
        int F07;
        int F08;
        int F09;
        int F10;
        int F11;
        int F12;
        int F13;
        F01 = int.Parse(GridView3.Rows[0].Cells[3].Text.Trim());
        F02 = int.Parse(GridView3.Rows[1].Cells[3].Text.Trim());
        F03 = int.Parse(GridView3.Rows[2].Cells[3].Text.Trim());
        F04 = int.Parse(GridView3.Rows[3].Cells[3].Text.Trim());
        F05 = int.Parse(GridView3.Rows[4].Cells[3].Text.Trim());
        F06 = int.Parse(GridView3.Rows[5].Cells[3].Text.Trim());
        F07 = int.Parse(GridView3.Rows[6].Cells[3].Text.Trim());
        F08 = int.Parse(GridView3.Rows[7].Cells[3].Text.Trim());
        F09 = int.Parse(GridView3.Rows[8].Cells[3].Text.Trim());
        F10 = int.Parse(GridView3.Rows[9].Cells[3].Text.Trim());
        F11 = int.Parse(GridView3.Rows[10].Cells[3].Text.Trim());
        F12 = int.Parse(GridView3.Rows[11].Cells[3].Text.Trim());
        F13 = int.Parse(GridView3.Rows[12].Cells[3].Text.Trim());
        cmd.CommandText = "Insert Into VendorExportTemplate (VendorNo,SourceID,ExportOption,F01,F02,F03,F04,F05,F06,F07,F08,F09,F10,F11,F12,F13) " +

           " values ('" + DVendor.SelectedValue + "','L','UserDefine','" + F01 + "','" + F02 + "','" + F03 + "','" + F04 + "','" + F05 + "','" + F06 + "','" + F07 + "','" + F08 + "','" + F09 + "','" + F10 + "','" + F11 + "','" + F12 + "','" + F13 + "')";
        cmd.ExecuteNonQuery();

        tr.Commit();
    }