/// <summary>
 /// Start device watcher.
 /// </summary>
 private void StartWatcher()
 {
     if (posDeviceWatcher == null)
     {
         posDeviceWatcher = new PosDeviceWatcher(BarcodeScanner.GetDeviceSelector(), Dispatcher);
         posDeviceWatcher.Start();
     }
 }
 /// <summary>
 /// Start device watcher.
 /// </summary>
 private void StartWatcher()
 {
     if (posDeviceWatcher == null)
     {
         posDeviceWatcher = new PosDeviceWatcher(BarcodeScanner.GetDeviceSelector(), Dispatcher);
         posDeviceWatcher.Start();
     }
 }