tbo.Parent = this;
  tbo.Multiline = true;
  tbo.Top = 50;
  tbo.Height = 200;
 
  String[] Files = System.IO.Directory.GetFiles("C:\\Daten", "*.*", 
       System.IO.SearchOption.TopDirectoryOnly);
 
   for (int i = 0; i <Files.Length; i++)
     {
        tbo.AppendText(Files);
        tbo.AppendText(Environment.NewLine);
     }