How does SetUnhandledExceptionFilter work in .NET WinForms applications?

Question

I am working on a project to enhance our production debugging capabilities. Our goal is to reliably produce a minidump on any unhandled exception, whether the exception is

Answer 1

Windows Forms has a built-in exception handler that does the following by default:

• Catches an unhandled managed exception when:
  • no debugger attached, and
  • exception occurs during window message processing, and
  • jitDebugging = false in App.Config.
• Shows dialog to user and prevents app termination.

You can disable the first behaviour by setting jitDebugging = true in App.Config. This means that your last chance to stop the app terminating is to catch the unhandled exception by registering for the event Application.ThreadException, e.g. in C#:

Application.ThreadException += new Threading.ThreadExceptionHandler(CatchFormsExceptions);

If you decide not to catch the unhandled exception here, then you will need to check and/or change the registry setting DbgJitDebugLaunchSetting under HKLM\Software.NetFramework. This has one of three values of which I'm aware:

• 0: shows user dialog asking "debug or terminate".
• 1: lets exception through for CLR to deal with.
• 2: launches debugger specified in DbgManagedDebugger registry key.

In Visual Studio, go to Tools>Options>Debugging>JIT to set this key to 0 or 2. But a value of 1 is usually what you want on an end-user's machine. Note that this registry key is acted on before the CLR unhandled exception event that you discuss.

Then you can set the native exception filter that you discussed.