สอบถามเรื่องการ replace ข้อมูลลงไปใน textfile อะครับ พอดี มันไม่ยอมเข้าไปในตำแหน่งที่ผมเขียนไว้

using System;
using System.Linq;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Globalization;

namespace ExcellenceSportHH
{
    public partial class frmCheckingSheet : Form
    {
        public frmCheckingSheet()
        {
            InitializeComponent();
        }

        private string _ValueLocationID;
        private string _ValueNameCheck;
        public string ValueLocationID
        {
            get
            {
                return this._ValueLocationID;
            }
            set
            {
                this._ValueLocationID = value;
            }
        }

        public string ValueNameCheck
        {
            get
            {
                return this._ValueNameCheck;
            }
            set
            {
                this._ValueNameCheck = value;
            }
        }

        public void LoadInfor()
        {
            StreamReader sr = new StreamReader("\\Program Files\\ExcellenceSportHH\\CheckStock.txt");
                      
                                string[] split = new string[11];
                                split = sr.ReadLine().Split(',');
            txtbarcode.Focus();
          
           
           
        }

        public void btnSave_Click(object sender, EventArgs e)
        {
            try
            {
                if (txtbarcode.Text == "")
                {
                    MessageBox.Show("Input your Barcode");
                    txtbarcode.Focus();
                }

                if (txtbarcode.Text != "")
                {
                    //StreamReader sr = new StreamReader("\\Program Files\\ExcellenceSportHH\\CheckStock.txt");
                    try
                    {
                        StreamReader sr = new StreamReader("\\Program Files\\ExcellenceSportHH\\CheckStock.txt");
                        do while (sr.Peek() > -1)
                            {
                                string[] split = new string[11];
                                split = sr.ReadLine().Split(',');
                                List<string> updateLines = new List<string>();
                               foreach (var line in sr.ReadLine())
                                {
                                    if (split[0] == txtbarcode.Text)
                                    {
                                        //update value จะให้ข้อมูลไปใส่แทนที่ในที่ครับ
                                        split[8] = (int.Parse(split[8]) + 1).ToString();
                                        split[9] = _ValueNameCheck;
                                        split[10] = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");
                                        
                                    }
                                    sr.Close();
แล้วค่ามันไม่ยอม update 
                                    updateLines.Add(string.Join(",", split));
                                    sr.Close();
                                }                              
                            } while (sr.ReadLine() != null);
                        sr.Close();
                    }
                    catch (Exception ex) { MessageBox.Show(ex.ToString()); }
                    MessageBox.Show("Complete...");

                    txtbarcode.Text = "";
                    txtVN.Text = "";
                    txtColor.Text = "";
                    txtSize.Text = "";
                    txtStyle.Text = "";
                    txtCollection.Text = "";
                    txtPrice.Text = "";
                    txtQtyAll.Text = "";
                    txtbarcode.Focus();
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
        }

        private void mnuLogout_Click(object sender, EventArgs e)
        {
            frmLogin backward = new frmLogin();
            backward.Show();
            this.Close();
        }

        private void txtbarcode_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Enter)
            {
                if (txtbarcode.Text != "")
                {
                    string[] split = new string[11];
                    //StreamReader sr = new StreamReader("\\Program Files\\CCL_ExcellenceSport\\CheckStock.txt");
                    StreamReader sr = new StreamReader("\\Program Files\\ExcellenceSportHH\\CheckStock.txt");

                    try
                    {
                        do while (sr.Peek() > -1 )
                        {
                            split = sr.ReadLine().Split(',');
                            string barcode = split[0];
                            if (string.Compare(barcode, txtbarcode.Text.Trim(), true) == 0)
                            {
                                //txtbarcode.Text = Barcode;
                                txtVN.Text = split[1];
                                txtStyle.Text = split[2];
                                txtColor.Text = split[3];
                                txtSize.Text = split[4];
                                txtPrice.Text = split[5];
                                txtCollection.Text = split[6];
                                txtQtyAll.Text = split[7];
                                btnSave.Focus();
                            }
                        } while (sr.ReadLine() != null);
                    }
                    catch (Exception ex)
                    {
                        MessageBox.Show(ex.ToString());
                    }
                }
                else
                {
                    MessageBox.Show("Not found this barcode, Plese check again!!");
                    txtbarcode.Focus();
                    txtbarcode.SelectAll();
                }
            }
        }

        private void mnuReport_Click(object sender, EventArgs e)
        {
            frmReport Nextpage = new frmReport();
            Nextpage.LocationCode = this._ValueLocationID;
            Nextpage.Show();
            this.Hide();
        }

        private void mnuExit_Click(object sender, EventArgs e)
        {
            Application.Exit();
        }

        private void frmCheckingSheet_Load(object sender, EventArgs e)
        {
            CultureInfo us = System.Globalization.CultureInfo.GetCultureInfo("en-US");
        }
    }
}