Trapping exceptions for logging in a C++ CLI app

Question

I'm trying to trap any and all exceptions in a C++/CLI app so that I can log and record them (including a stack trace). So far I have some code which looked promising:

[STAThreadAttribute]
int main(array<System::String ^> ^args)
{
 // Enabling Windows XP visual effects before any controls are created
 Application::EnableVisualStyles();
 Application::SetCompatibleTextRenderingDefault(false); 

 // Create the main window and run it
 try
 {
  Application::Run(gcnew MainForm());
 }
 catch( System::Exception^ e )
 {
  String^ message = gcnew String("");
  System::Exception^ exceptionRecursor = e;

  message = "ERROR: Uncaught exception encountered!\n\n";
  while( exceptionRecursor )
  {
   message += exceptionRecursor->Source+"\n\t";
   message += exceptionRecursor->Message+"\n\t";
   message += exceptionRecursor->StackTrace+"\n\n";
   exceptionRecursor = exceptionRecursor->InnerException;
  }
  MessageBox::Show(message);
 }

 return 0;
}

...but instead of disaplying a dialog box with my tidied up errors, I get something else:

An unhandled exception of type 'System.Reflection.TargetInvocationException' occurred in mscorlib.dll

Additional information: Exception has been thrown by the target of an invocation.

Is this because the Run command is trying to deal with the exception in some way? Do I need to handle things inside MainForm somewhere? ...or is there some other (better) way of going about this.

Forgetting the source of the error for a moment (I'm mid development cycle and still debugging), it would be nice to be able to trap these errors and produce a neat little stack trace which could remain in the code right up to deployment and let users us know when things are going wrong. Eventually I'd wrap the error report into something that could report over the web.

Answer 1

If the reflection is happening in a different thread, the wrapper isn't going to catch it failing.

Answer 2

I found a solution (using Application::ThreadException):

// Creates a class to throw the error.
public:
   ref class ErrorHandler: public System::Windows::Forms::Form
   {
   // Inserts the code to create a form with a button.

   // Programs the button to throw an exception when clicked.
   private:
   void button1_Click( Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
   throw gcnew ArgumentException( "The parameter was invalid" );
   }

   public:
   static void Main()
   {
   // Creates an instance of the methods that will handle the exception.
   CustomExceptionHandler ^ eh = gcnew CustomExceptionHandler;

   // Adds the event handler to to the event.
   Application::ThreadException += gcnew ThreadExceptionEventHandler( eh, &Form1::CustomExceptionHandler::OnThreadException );

   // Runs the application.
   Application::Run( gcnew ErrorHandler );
   }
   };

// Creates a class to handle the exception event.
internal:
   ref class CustomExceptionHandler
   {
   // Handles the exception event.
   public:
   void OnThreadException( Object^ /*sender*/, ThreadExceptionEventArgs^ t )
   {
   System::Windows::Forms::DialogResult result = ::DialogResult::Cancel;
   try
   {
   result = this->ShowThreadExceptionDialog( t->Exception );
   }
   catch ( Exception^ ) 
   {
   try
   {
      MessageBox::Show( "Fatal Error", "Fatal Error", MessageBoxButtons::AbortRetryIgnore, MessageBoxIcon::Stop );
   }
   finally
   {
      Application::Exit();
   }
   }

   // Exits the program when the user clicks Abort.
   if ( result == ::DialogResult::Abort )
   {
   Application::Exit();
   }
   }

   // Creates the error message and displays it.
   private:
   System::Windows::Forms::DialogResult ShowThreadExceptionDialog( Exception^ e )
   {
   String^ errorMsg = "An error occurred please contact the adminstrator with the following information:\n\n";
   errorMsg = String::Concat( errorMsg, e->Message, "\n\nStack Trace:\n", e->StackTrace );
   return MessageBox::Show( errorMsg, "Application Error", MessageBoxButtons::AbortRetryIgnore, MessageBoxIcon::Stop );
   }
   };