Unhandled exception in an even handler code block

I am coding a DLL in C++/CLI that is called in a C# based GUI application. I throw a custom exception (derived from Exception class), which, if not swallowed in my DLL, is handled in the final catch block in the GUI code. It works well for all throws, save one:

Im my DLL I have implemented a handler that will listen to SerialPort::DataReceived events. If I get an incorrect packet, I raise a custom exception, which is rethrown in the outermosst try-catch block. The GUI is supposed to display this custom exception. But for some reason an exception raised in this block is not re-thrown. Instead I get an "Unhandled exception" message in Debug mode. When I run the exe directly by double clicking the exe (in release folder) it simply crashes. Apparently, exceptions raised in this event handler method are not handled by the GUI. Or maybe they are not passed to the GUI from my DLL. It doesnt create a problem for other parts of my dll. The only reason I can think for this different behaviour is that the event handler doesn't have a caller. Is my guess correct? or is there some other reason. Any clues on how I can handle this problem? I dont want my application to crash. I just want 开发者_高级运维to raise an exception so that the message can be displayed to the user in the GUI and the application can stop communicating with the serial port.

You need to switch to the UI thread before throwing from that event handler. This is typically accomplished with System::Threading::SynchronizationContext, but if you're using WinForms you can alternatively use System::Windows::Forms::Control::BeginInvoke or System::Windows::Forms::Control::Invoke.