Silverlight OOB Read COM port data received eventhandler crashes

Question

I'm trying read data of RFID scanner using Silverlight4. I know I can do so as Silverlight4 supports reading client COM ports in OOB mode and using Elevated permissions.

RFID scanner works fine when I read the data by simple win app however when I did the same with a silverlight app I get an exception when Datareceived event is called I have no clue why this happen. below is the code I have

P.S: I'm using the below library to access serialports from silverlight https://interopcom.codeplex.com/

 private void button1_Click(object sender, RoutedEventArgs e)
    {
      if (Application.Current.IsRunningOutOfBrowser /*&& Application.Current.HasElevatedPermissions*/)
      {
          SerialPort sp1 = new SerialPort("COM7");
          sp1.BaudRate = 9600;
          sp1.Parity = Parity.None;
          sp1.StopBits = StopBits.One;
          sp1.DataBits = 8;
          sp1.Handshake = Handshake.None;
          sp1.DataReceived += new SerialDataReceivedEventHandler(sp1_DataReceived);
          sp1.Open();
          MessageBox.Show("opened");
      }
    }


    private static void sp1_DataReceived(object sender, SerialDataReceivedEventArgs e)
    {

      SerialPort sp2 = sender as SerialPort;
      MessageBox.Show(sp2.ReadLine());
      sp2.Close();
      MessageBox.Show("closed");
    }