Problem filtering using a datatable

I got an application which display all files in a given directory. And now I want to implement a search function within the application. I use the textBox_textChanged method to implement the search as it is faster. But somehow I cannot get it to work. It won't filter the datagridview even when values is entered into the textbox. I don't know what's the problem. Here is my code :
 

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

namespace MonitorDirectory
{
    public partial class Form1 : Form
    {   private Timer timer;
        private int count;
        DataTable dt = new DataTable();
        DataRow dr;
        String[] s1;
        public Form1()
        {
            InitializeComponent();
        }
 

        private void Form1_Load(object sender, EventArgs e)
        {   
            count = 0;
            timer = new Timer();
            timer.Interval = 1000;
            timer.Tick += new EventHandler(timer1_Tick);
            timer.Start();
            s1 = Directory.GetFiles(@"C:\Documents and Settings\Administrator\Desktop\FILE","*.*",SearchOption.AllDirectories);
            for (int i = 0; i <= s1.Length - 1; i++)
            {
                if (i == 0)
                {
                    dt.Columns.Add("File_Name");
                    dt.Columns.Add("File_Type");
                    dt.Columns.Add("File_Size");
                    dt.Columns.Add("Create_Date");
                }
 
                //Get each file information
                FileInfo info = new FileInfo(s1[i]);
                FileSystemInfo sysInfo = new FileInfo(s1[i]);
                dr = dt.NewRow();
                //Get File name of each file name
                dr["File_Name"] = sysInfo.Name;
                //Get File Type/Extension of each file 
                dr["File_Type"] = sysInfo.Extension;
                //Get File Size of each file in KB format
                dr["File_Size"] = (info.Length / 1024).ToString();
                //Get file Create Date and Time 
                dr["Create_Date"] = sysInfo.CreationTime.Date.ToString("dd/MM/yyyy");
                //Insert collected file details in Datatable
                dt.Rows.Add(dr);
                //
              
                
                if ((info.Length / 1024) > 5000)
                {
                   MessageBox.Show("" + sysInfo.Name + " had reach its size limit.");
                }
            }
            if (dt.Rows.Count > 0)
            {
                //Finally Add DataTable into DataGridView
                dataGridView1.DataSource = dt;
            } 
        }
 
        private void timer1_Tick(object sender, EventArgs e)
        {
                count++;
                if (count == 300)
                {
                    count = 0;
                    timer.Stop();
                    Application.Restart();
                }
        }
        public string secondsToTime(int seconds)
        {
             int minutes = 0;
             int hours = 0;
 
             while (seconds >= 60)
             {
                minutes += 1;
                seconds -= 60;
             }
             while (minutes >= 60)
             {
                hours += 1;
                minutes -= 60;
             }
 
             string strHours = hours.ToString();
             string strMinutes = minutes.ToString();
             string strSeconds = seconds.ToString();
 
             if (strHours.Length < 2)
                 strHours = "0" + strHours;
             if (strMinutes.Length < 2)
                 strMinutes = "0" + strMinutes;
             if (strSeconds.Length < 2)
                 strSeconds = "0" + strSeconds;
             return strHours + ":" + strMinutes + ":" + strSeconds;
         }
 
        //This is the filtering part of the program.
        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            DataRow[] dr = dt.Select("File_Name like '%" + textBox1.Text + "%'");
        }
   }
}