How I can compare Items in listBox to files in folder(listbox items=>re4506s.pdf, files in a folder =>re4506s.pdf)

private void btnPrint_Click(object sender, EventArgs e) {
//FolderBrowserDialog fbg = new FolderbrowserDialog();

//if (fbd.ShowDialog() == DialogResult.Ok) {
    string dir = @"C:\slimeyyyy";
    if (Directory.Exists(dir)) {
        string[] files = Directory.GetFiles(dir);
        if (files.Length > 0) {

            // To print documents in any order based on the current file
            foreach (string file in files) {
                string fileName = Path.GetFileName(file);
                foreach (object item in listBox1.Items) {
                    if (fileName == item.ToString()) {
                        PrintDocument(Path.GetFullPath(file));
                    }
                }
            }

            // To print documents starting with the first item in the list box.
            for (int i = 0; i < listBox1.Items.Count; i++) {
                foreach (string file in files) {
                    string fileName = Path.GetFileName(file);
                    if (fileName == listBox1.Items[i].ToString()) {
                        PrintDocument(Path.GetFullPath(file));
                    }
                }
            }
        }
    }
}

private void PrintDocument(string path) {
    ProcessStartInfo info = new ProcessStartInfo();
    info.Verb = "print";
    info.FileName = path;
    info.CreateNoWindow = true;
    info.WindowStyle = ProcessWindowStyle.Hidden;

    Process p = new Process();
    p.StartInfo = info;
    p.Start();

    p.WaitForInputIdle();
    System.Threading.Thread.Sleep(3000);
    if (!p.CloseMainWindow()) {
        p.Kill();
    }
}