[C#] I wish I knew : catch unhandled exceptions

04 December 2013 i-wish-i-knew, csharp, i-wish-i-knew-2

I’ve been a professional C# developer for years now, but I’m still discovering trivial stuffs. In “I wish I knew”, I describe a feature that I missed.

Here is a very common pattern: I’m writing an application and I want a custom dialog box to appear in case an unhandled exception occurs (and unfortunately this happens quite often ;-).

However, I don’t want this dialog to pop out when i’m debugging. I still want Visual Studio to show me the source of the exception.

My old way to do it

To do so, I used to write cumbersome codes like:

static class Program
{
    static void Main()
    {
#if DEBUG
        MainCore();
#else
        try
        {
            MainCore();
        }
        catch (Exception e)
        {
            MessageBox.Show(e.ToString());
        }
#endif
    }

    private static void MainCore()
    {
       // do the actual job here
    }
}

So that the try/catch is only compiled in the “Release” configuration.

My new way to do it

I recently discovered that you can reach the same goal with a clever use of:

1. AppDomain.CurrentDomain.UnhandledException
2. System.Diagnostics.Debugger.IsAttached

Here is the new version of the above code:

class Program
{
    static void Main(string[] args)
    {
        AppDomain.CurrentDomain.UnhandledException += OnUnhandledException;

        // do the actual job here
    }

    static void OnUnhandledException(object sender, UnhandledExceptionEventArgs e)
    {
        if (Debugger.IsAttached) return;
        
        MessageBox.Show(e.ExceptionObject.ToString());
        Environment.Exit(1);
    }
}

I really prefer this solution for the following reasons:

1. No MainCore() method
2. No #if
3. No ReSharper complaining about unused code and using
4. Works in both “Release” and “Debug” configurations

If you want to see how to do the same in Windows Forms or in WPF, see sample projects on GitHub