void startReader()
 {
     if (BarcodeReader == null)
     {
         BarcodeReader = new BarcodeReaderApi();
         BarcodeReader.onBarcodeReadEvent += BarcodeReader_onBarcodeReadEvent;
     }
 }
 void stopReader()
 {
     if (BarcodeReader != null)
     {
         BarcodeReader.onBarcodeReadEvent -= BarcodeReader_onBarcodeReadEvent;
         BarcodeReader.Dispose();
         BarcodeReader = null;
     }
 }