Value cannot be null POS.NET V1.12 Barcode Scanner

class bScan
{
    public PosExplorer explorer;
    public  Scanner scanner;
    string BarCodeReader;

    public  void  Start_Scan()
    {         
        //  explorer = new PosExplorer();
        // explorer.DeviceAddedEvent += new DeviceChangedEventHandler(explorer_DeviceAddedEvent);
        // var device=explorer.GetDevice(DeviceType.Scanner);
        ;
    }

    public void read()
  //  public   void explorer_DeviceAddedEvent(object sender,DeviceChangedEventArgs e)
    {
        explorer = new PosExplorer();
        DeviceInfo device = explorer.GetDevice("Scanner",BarCodeReader);
        this.scanner =(Scanner)explorer.CreateInstance(device);
        this.scanner.Open();
        this.scanner.Claim(1000);
        this.scanner.DeviceEnabled = true;
        this.scanner.DataEvent += new DataEventHandler(scanner_DataEvent);
        this.scanner.DataEventEnabled = true;
        this.scanner.DecodeData = true;   
    }
        //}
  
    public  void scanner_DataEvent(object sender,DataEventArgs e)
    {
        string data;
        ASCIIEncoding encoding=new ASCIIEncoding();
        scanner.DataEventEnabled=true;         
        data=encoding.GetString(scanner.ScanDataLabel);
        // listBox1.Items.Add(encoding.GetString(scanner.ScanDataLabel));     
    }

}