What causes my UI to freeze when closing a serial port?

Question

I am working on a serial port related application. While using DataReceived event of SerialPort I need to update a textbox with the received bytes:

Answer 1

The problem could be solved by adding a timer:

  bool formClosing = false;
    private void Connection_DataReceived(object sender, SerialDataReceivedEventArgs e)
    {
      if (formClosing) return;
      _buffer = Connection.ReadExisting();
      Invoke(new EventHandler(AddReceivedPacketToTextBox));
    }
    protected override void OnFormClosing(FormClosingEventArgs e)
    {
      base.OnFormClosing(e);
      if (formClosing) return;
      e.Cancel = true;
      Timer tmr = new Timer();
      tmr.Tick += Tmr_Tick;
      tmr.Start();
      formClosing = true;
    }
    void Tmr_Tick(object sender, EventArgs e)
    {
      ((Timer)sender).Stop();
      this.Close();
    }

Thanks to JohnWein from MSDN