How to search image in listview through searchbox

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C#3.5

ListView

The problem occurs in text_changed event, when the user types a character, the resultant image is received with only text, while the image is blank. After finishing the search, all images become blank while the text restores back. Here , the searchbox is a textbox.

using MetroFramework.Forms;
using System;
using System.Collections.Generic;
using System.Drawing;
using System.IO;
using System.Windows.Forms;

namespace DocumentViewer
{
    public partial class ImageForm : MetroForm
    {
        private string[] files = new string[] { };
        private TreeForm dialog;
        private List<string> filePath = new List<string>();
        private ListViewItem lstItem;
        private int index;

        public ImageForm()
        {
            InitializeComponent();
        }

        private void browseButton_Click(object sender, System.EventArgs e)
        {
            dialog = new TreeForm();

            dialog.FileFilter = "IMG";
            if (dialog.ShowDialog() == DialogResult.OK)
            {
                try
                {
                    listView1.Cursor = Cursors.WaitCursor;
                    clear();
                    searchBox.Enabled = true;
                    files = dialog.SelectedPath;

                    foreach (string temp in files)
                    {
                        Image image = Image.FromFile(temp);
                        Image thumbNail = image.GetThumbnailImage(100, 100,      
                                                           null, new IntPtr());
                        filePath.Add(Path.GetFileNameWithoutExtension(temp));
                        imageList1.Images.Add(thumbNail);
                        fileLabel.Text = "Files : " + imageList1.Images.Count;
                    }
                    loadCaption();
                    listView1.LargeImageList = imageList1;
                    
                    listView1.Cursor = Cursors.Hand;
                }
                catch (Exception error)
                {
                    MessageBox.Show(error.Message);
                }
            }
        }

        private void loadCaption()
        {
            for (int j = 0; j < imageList1.Images.Count; j++)
            {
                lstItem = new ListViewItem();
                lstItem.ImageIndex = j;
                lstItem.Text = Path.GetFileNameWithoutExtension(filePath[j]);
                listView1.Items.Add(lstItem);
            }
        }
        private void clear()
        {
            listView1.Clear();
            lstItem = null;
            imageList1.Images.Clear();
            fileLabel.ResetText();
            pictureBox1.Image = null;
            searchBox.ResetText();
            filePath.Clear();
        }

        private void listView1_ItemChecked(object sender, ItemCheckedEventArgs e)
        {
            try
            {
                if (e.Item.Checked == true)
                {
                    index = Array.FindIndex(files, files => 
                                            files.Contains(e.Item.Text));
                    pictureBox1.Image = Image.FromFile(files[index]);
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

        private void searchBox_TextChanged(object sender, EventArgs e)
        {
            listView1.Items.Clear();

            foreach (string str in files)
            {
                    if (str.ToUpper().Contains(searchBox.Text.ToUpper()) == true)
                    {

                        listView1.Items.Add(Path.GetFileName(str));
                    }
            }
        }

        private void toolStripMenuItem1_Click(object sender, EventArgs e)
        {
            listView1.View = View.LargeIcon;
        }

        private void toolStripMenuItem2_Click(object sender, EventArgs e)
        {
            listView1.View = View.SmallIcon;
        }
    }
}

What I have tried:

 private void searchBox_TextChanged(object sender, EventArgs e)
       {
           listView1.Items.Clear();

           foreach (string str in files)
           {
                   if (str.ToUpper().Contains(searchBox.Text.ToUpper()) == true)
                   {
// This assigns only the last image index to the searched image as well as rest of the images
                       listView1.Items.Add(Path.GetFileName(str),
                                           lstItem.ImageIndex);
                   }
           }
       }