Insert from Generic List into database not working on ASP.Net Button Click using C#

On button click no values inserts into the database.

When i Response.Write the (insertSQL ) i got this message

INSERT INTO tracking (stockid,packinglist,datesent,location,comment,status) VALUES (@stockid,@packinglist,@datesent,@location,@comment,@status)
INSERT INTO tracking (stockid,packinglist,datesent,location,comment,status) VALUES (@stockid,@packinglist,@datesent,@location,@comment,@status)
INSERT INTO tracking (stockid,packinglist,datesent,location,comment,status) VALUES (@stockid,@packinglist,@datesent,@location,@comment,@status)

protected void Button1_Click(object sender, EventArgs e)
{
    List<string> stockid = (List<string>)Session["id"];

    int added = 0;
    for (int i = 0; i < stockid.Count; i++)
    {
        string insertSQL = "INSERT INTO tracking (stockid,packinglist,datesent,location,comment,status) VALUES (@stockid,@packinglist,@datesent,@location,@comment,@status)";
        String connectionString = "data source=NERO-SIGBENU\\SQLEXPRESS01; Initial Catalog=arpackaging;Integrated Security=True;";
        SqlConnection con = new SqlConnection(connectionString);
        SqlCommand cmd = new SqlCommand(insertSQL, con);
        cmd.Parameters.AddWithValue("@stockid", stockid[i]);
        cmd.Parameters.AddWithValue("@packinglist", TextBox1.Text);
        cmd.Parameters.AddWithValue("@datesent", Session["Time1"].ToString());
        cmd.Parameters.AddWithValue("@location", DropDownList1.SelectedItem.ToString());
        cmd.Parameters.AddWithValue("@comment", TextBox2.Text);
        cmd.Parameters.AddWithValue("@status", 1);
        try
        {
            con.Open();
            Response.Write(insertSQL);
            added += cmd.ExecuteNonQuery();
        }
        catch (Exception)
        {

        }
        finally
        {
            con.Close();
        }
    }
}