NullReferenceException, no stack trace... where to start?
c#, debugging, pinvoke, winmm, wpf
Solution
The most helpful thing you can do in the debugger is instruct it to break on a first-chance exception (Debug -> Exceptions):
This will cause a break into the debugger at the exact point a `NullReferenceException` is thrown, which is pretty much the best you can ever hope for while debugging.
Problem
I have a WPF audio application. Occasionally (and even in the debugger) I'm seeing a `NullReferenceException` which carries no stack trace information with it. How can one start debugging such an issue? Some background: I'm P/Invoking functions in `WinMM.dll` which involves registering a callback when calling `waveOutOpen` ``` [DllImport("winmm.dll")] public static extern MmResult waveOutOpen(out IntPtr phwo, IntPtr uDeviceID, WaveFmt pwfx, WaveCallbk dwCallback, IntPtr dwInstance, int fdwOpen); ``` This has proved difficult to get stable, especially at the point where I call `waveOutClose`, and immediately call `waveOutOpen` again (usually to change the output format). I suspect that the problem may be related to the calls I've been describing above (although on so little knowlege, I could be completely off-target). Reproducing the problem is currently proving elusive, although I can supply a build to a user who is fairly consistently seeing this problem. I might try to speed up the operations that are causing the problem to the point where reproducing the problem in the debugger is more of a certainty. With regards to the debugger, I haven't tinkered with any of the settings (including `Enable unmanaged code debugging`) or any of the `Debug -> Exceptions...` settings. To be honest, I'm fairly clueless about what's on offer here, so any hints are welcome. How might an exception not have a stack trace? Have you seen this before? Help!