About List Box and update command

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C#

string query = string.Format("update Product set BalanceOnStock='{0}' where ProHead='{1}'", value.ToString(), ddlItem);

It's still not working please assist me for the same i am sending you the whole coding of the same page...

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;


public partial class DailyComsumption : System.Web.UI.Page
{
    SqlConnection cn;
    SqlCommand cm;
    //SqlConnection conn = null;
    //Sqlmmand cmd = new SqlCommand(conn);
    int abc, dal, insert, showdata, baldata,updatebal,updateitem;
    int item;

    protected void Page_Load(object sender, EventArgs e)
    {
        string cs = @"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=true;User Instance=true";
        cn = new SqlConnection(cs);
        cn.Open();
    }
   
   
    protected void BtPrint_Click(object sender, EventArgs e)
    {
        Response.Redirect("Report.aspx");
    }

    protected void TxtWorkSelection_TextChanged(object sender, EventArgs e)
    {

    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        
//string ddlItem = "";
//if (DDLItem.SelectedItem != null)
//{
//   // ddlItem = (Cast to whatever type it is) DDLItem.SelectedItem.Text;
//}
//if (ddlItem != "")
//{
    //try
    //{
    //    conn = new SqlConnection(connectionString);
    //    cmd = new SqlCommand(conn);
    //    cmd.CommandType = CommandType.Text;
    //    foreach (ListItem LBox4Item in ListBox4.Items)
    //    {
    //        ListBox5.Items.Add(LBox4Item);
    //        int value = LBox4Item.ToString();
    //        // In the code you originally posted, you're adding everything in Listbox5 everytime 
    //        // you add something to Listbox5. I'm almost positive this isn't what you wanted to to.
    //        // So, just add the item that was recently added.
    //        string query = string.Format("update Product set BalanceOnStock='{0}' where ProHead='{1}'", value.ToString(), ddlItem);
    //        cmd.CommandText = query;
//            cmd.ExecuteNonQuery();
//        }
//    }
//    catch(Exception ex)
//    {
//        // determine your exception here
//    }
//    finally
//    {
//        if (conn != null)
//        {
//            conn.Close();
//        }
//    } 
//}
        foreach (ListItem LBox4Item in ListBox4.Items)
        {
            ListBox5.Items.Add(LBox4Item);
            int value = Convert.ToInt32( LBox4Item.ToString());
            //updateitem = Convert.ToInt32(LBox5Item.ToString());
            //string q = "update Product set BalanceOnStock='{0}' where ProHead='{1}'", value.oString(), DDLItem;
            //"update Product set BalanceOnStock='" + updateitem.ToString() + "' where ProHead='" + DDLItem.SelectedItem.Text + "'";
            string query = string.Format("update Product set BalanceOnStock='{0}' where ProHead='{1}'", value.ToString(), DDLItem);
            cm = new SqlCommand(query, cn);
            cm.ExecuteNonQuery();
        }                                                            
    }

    protected void  DDLItem_SelectedIndexChanged(object sender, EventArgs e)
        {
        string q = "select QuantityforAssembly, BalanceOnStock from Product where ProHead ='" + DDLItem.SelectedItem.Text + "'";
        cm = new SqlCommand(q, cn);
        SqlDataReader r = cm.ExecuteReader();
        while (r.Read())
        {

            ListBox1.Items.Add(r.GetString(0));
            ListBox2.Items.Add(r[1].ToString());

        }        
        foreach (ListItem LBoxItem in ListBox1.Items)
        {
            abc = Convert.ToInt32(LBoxItem.ToString());
            insert = Convert.ToInt32(TxtWorkSelection.Text);
            dal = Convert.ToInt32(abc * insert);
            ListBox3.Items.Add(dal.ToString());
        }

             
            foreach (ListItem LBox3Item in ListBox3.Items)
            {
                foreach (ListItem LBox2Item in ListBox2.Items)
                {

                    baldata = Convert.ToInt32(LBox2Item.ToString());
                    showdata = Convert.ToInt32(LBox3Item.ToString());
                    updatebal = baldata - showdata;
                }
                ListBox4.Items.Add(updatebal.ToString());
            }                           
        }

        

    protected void BtGenReport_Click(object sender, EventArgs e)
    {        
     //foreach (ListItem LBox4Item in ListBox4.Items)
     //   {
     //       item = Convert.ToInt32(LBox4Item.ToString());
     //       ListBox5.Items.Add(item.ToString());            
     //   }
    


    }
    protected void ListBox4_SelectedIndexChanged(object sender, EventArgs e)
    {

    }
    protected void BtClear_Click(object sender, EventArgs e)
    {
        //foreach (ListItem LBoxDelItem in ListBox1.Items)
        //{
        //    ListBox1.Items.Remove(LBoxDelItem.ToString());
        //}
    }
}

Please go to step wise step and give me the solution if possible

The last item value was updated and add to the database each row for example 4910,4910,4910,4910,4910,4910,4910,4910,4910,4910,4910 till statement of for each get not get false.