Question

I have 2 forms, one is MainForm and second is DebugForm. The MainForm has a button that sets up and shows the DebugForm like this, And passes a reference to an already opened SerialPort:

private DebugForm DebugForm; //Field
private void menuToolsDebugger_Click(object sender, EventArgs e)
{
    if (DebugForm != null)
    {
        DebugForm.BringToFront();
        return;
    }

    DebugForm = new DebugForm(Connection);

    DebugForm.Closed += delegate
    {
        WindowState = FormWindowState.Normal;
        DebugForm = null;
    };

    DebugForm.Show();
}

In the DebugForm, I append a method to handle the DataReceived event of the serialport connection (in DebugForm’s constructor):

public DebugForm(SerialPort connection)
{
    InitializeComponent();
    Connection = connection;
    Connection.DataReceived += Connection_DataReceived;
}

Then in the Connection_DataReceived method, I update a TextBox in the DebugForm, that is using Invoke to do the update:

private void Connection_DataReceived(object sender, SerialDataReceivedEventArgs e)
{           
    _buffer = Connection.ReadExisting();
    Invoke(new EventHandler(AddReceivedPacketToTextBox));
}

But I have a problem. As soon as I close the DebugForm, it throws an ObjectDisposedException on the Invoke(new EventHandler(AddReceivedPacketToTextBox)); Line.

How can I fix this? Any tips/helps are welcome!

UPDATE

I found out if I remove the event in a button event click , and close the form in that button click, everything is fine and my debugform gets closed without any exception…how odd!

private void button1_Click(object sender, EventArgs e)
{
    Connection.DataReceived -= Connection_DebugDataReceived;
    this.Close();
}

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