Something

        private void button1_Click(object sender, EventArgs e)
        {
            listView1.Items.Clear();
            FolderBrowserDialog Folder = new FolderBrowserDialog();
            Folder.ShowDialog();
            string Search = "*";
            if (textBox1.Text.Length > 0)
                Search = textBox1.Text;
            System.IO.DirectoryInfo Mappe = new System.IO.DirectoryInfo(Folder.SelectedPath.ToString());
            foreach (System.IO.FileInfo Fil in Mappe.GetFiles("*"+Search+"*"))
            {
                listView1.Items.Add(Fil.Name);
                listView1.Items[listView1.Items.Count-1].SubItems.Add(Fil.Length.ToString());
            }