i’m having an issue with my code, i’m trying to add items from directory to listbox, the issue is i keep getting the same items (doplucate) over and over again

here is my code

String[] filesDir = Directory.GetFiles(@"C:FOLDER");
foreach (string file in filesDir)
  if (!this.listbox1.Items.Contains(file ))
  {
    listbox1.Items.Add(Path.GetFileNameWithoutExtension(file ) + @"  found");
  }