How to: Define and Install a Global Exception Handler
The following code example demonstrates how unhandled exceptions can be captured. The example form contains a button that, when pressed, performs a null reference, causing an exception to be thrown. This functionality represents a typical code failure. The resulting exception is caught by the application-wide exception handler installed by the main function.
This is accomplished by binding a delegate to the ThreadException event. In this case, subsequent exceptions are then sent to the App::OnUnhandled method.
Example
// global_exception_handler.cpp
// compile with: /clr
#using <system.dll>
#using <system.drawing.dll>
#using <system.windows.forms.dll>
using namespace System;
using namespace System::Threading;
using namespace System::Drawing;
using namespace System::Windows::Forms;
ref class MyForm : public Form
{
Button^ b;
public:
MyForm( )
{
b = gcnew Button( );
b->Text = "Do Null Access";
b->Size = Drawing::Size(150, 30);
b->Click += gcnew EventHandler(this, &MyForm::OnClick);
Controls->Add(b);
}
void OnClick(Object^ sender, EventArgs^ args)
{
// do something illegal, like call through a null pointer...
Object^ o = nullptr;
o->ToString( );
}
};
ref class App
{
public:
static void OnUnhandled(Object^ sender, ThreadExceptionEventArgs^ e)
{
MessageBox::Show(e->Exception->Message, "Global Exeception");
Application::ExitThread( );
}
};
int main()
{
Application::ThreadException += gcnew
ThreadExceptionEventHandler(App::OnUnhandled);
MyForm^ form = gcnew MyForm( );
Application::Run(form);
}