public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            List<AudioDevice> devices = new List<AudioDevice>();
            devices.Add(new AudioDevice() { Name= "MP4 Audio1", Direction="direction1"});
            devices.Add(new AudioDevice() { Name= "MP4 Audio2", Direction = "direction1" });
            devices.Add(new AudioDevice() { Name= "MP4 Audio3", Direction = "direction2" });
            devices.Add(new AudioDevice() { Name= "MP4 Audio4", Direction = "direction2" });
            devices.Add(new AudioDevice() { Name = "MP4 Audio5", Direction = "direction1" });

            ListCollectionView lcv = new ListCollectionView(devices);
            lcv.GroupDescriptions.Add(new PropertyGroupDescription("Direction"));
            this.cb.ItemsSource = lcv;
        }
    }
   public class AudioDevice
   {
    public string Name { get; set; }
    public string Direction { get; set; }
    public string Id { get; set; }
    public bool Default { get; set; }
        public override string ToString()
        {
            return Name;
        }
    }