Safe handle has been closed appears on program exit

[yeah1000]

Hello, i sometimes get the "Safe handle has been closed" exception when i CLOSE my application (in debug mode). When i run it from the exe and try to close the app i simple get the "program has stopped working" error. I use a com port to communicate with an external device. I hear it has something to do with a .net bug but is there anything i can do in the Form_closing event perhaps or somewhere else to stop it from showing when i close my program. How could i handle that exception? Heres the stack trace: System.ObjectDisposedException was unhandled Message="Safe handle has been closed" Source="mscorlib" ObjectName="" StackTrace: at Microsoft.Win32.Win32Native.SetEvent(SafeWaitHandle handle) at System.Threading.EventWaitHandle.Set() at System.IO.Ports.SerialStream.AsyncFSCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOverlapped) at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP) InnerException: My idea was the following: (to make sure that the communication thread does not send anything else when user wants to exit) Form_Closing event { signal_comm_thread loop while(getSignal_from_comm_thread) } Comm_thread { if(signal_received) signal_Form_Closing event break; } But the program wont close at all this way :( Tried to use ManualResetEvents, public static variables for the signaling but nothing helps. Only way the program closes is if i add a "MessageBox.Show" in Form_Closing event after signaling comm_thread. How can that help? TY

[Alan N]

I've seen similar things happens when attempting to close a serial port read thread at form close. What I do now is allow the reader thread to close the port and wait in the UI thread until the reader thread has exited. Like this:

private void ReadWriteThreadProc() {
  continueLooping = 1;
  try {
    while (continueLooping != 0) {
      try {
        received = com.Read(buffer, 0, buffer.Length);
        // process buffer etc.
      } catch (TimeoutException) {
        // do timeout related stuff
      }
    }
  } finally {
    com.Close();
  }
}

public void CloseCom() {
  Interlocked.Exchange(ref continueLooping, 0);
  ReadWriteThread.Join();
}

The timeout is rather crucial as it ensures that the exit condition is polled. Alan.

[supercat9]

Are you using a serial port, or a USB-to-serial converter? The SerialPort object in .Net does not behave well at all if a port is open on a USB-to-serial converter that is unplugged. I don't know any good libraries, but I'm sure they're out there. For my application, I coded a silly little helper application which acts as a bridge between a TCP socket and a .net SerialPort object; if the SerialPort object dies, the helper application quits without jinxing the main app.