Question

I’m trying to catch all unhandled exceptions in my app in order to conditionally handle those that can be without terminating the app, but I cannot solve a very basic problem: it doesn’t stop the exception. An unhandled exception is thrown somewhere in the code, it comes here, the message box is shown, and then the application either shows that the same exceptions was unhandled (if in debug mode) or just crashes (if run without debugging). Meaning that the exception stays unhandled even though the handler was called.

App() {
    AppDomain.CurrentDomain.UnhandledException += (s, a) => {
        var ex = (Exception)a.ExceptionObject;
        MessageBox.Show(ex.Message, "Error", MessageBoxButton.OK, MessageBoxImage.Error);
    };
}

This is from a new, blank test project that has nothing in it but this code and a button that throws exception when clicked.

Answer 1

From MSDN:

This event provides notification of uncaught exceptions. It allows the application to log information about the exception before the system default handler reports the exception to the user and terminates the application. If sufficient information about the state of the application is available, other actions may be undertaken — such as saving program data for later recovery. Caution is advised, because program data can become corrupted when exceptions are not handled.

In other words, it’s just a handler to allow you to tell the user what happened, produce last minute save information if you need to be able to recover data, or do something like fire off a custom error report. It is not a catch block. To catch exceptions you have to use Try-Catch.