Why does Raygun on .NET Native cause my app to crash?

I'm working on a Windows 10 Store application where I'm using Raygun.io (5.2.0). We released the app couple of times (latest in mid December) I see in Rayguns web interface the logs coming from previous versions. While testing the app now before publishing next version I found out that Raygun is not working anymore (= crashing) when sending exceptions if app is build using .NET native toolchain. I can reproduce this in a simple UWP test app:

public sealed partial class MainPage : Page
{
    //private readonly RaygunClient _raygunClient;

    public MainPage()
    {
        InitializeComponent();

        RaygunClient.Attach("<app_key>");
        //_raygunClient = new RaygunClient("<app_key>");
    }

    private async void OnClick(object sender, RoutedEventArgs e)
    {
        try
        {
            // this is crashing the app when project is build using .NET native toolchain
            // it is not even throwing exception
            //await _raygunClient.SendAsync(new InvalidOperationException("Raygun Test"));
            await RaygunClient.Current.SendAsync(new InvalidOperationException("Raygun Test")); // (1)
            Status.Text = "Ok";
        }
        catch (Exception exception) // (2)
        {
            Status.Text = $"Failed with {exception.Message}";
        }
    }
}

Checking https://github.com/MindscapeHQ/raygun4net supported platforms/frameworks, it doesn't seem to support explicitly UWP.

UPDATE: The application is killed after line (1), there is no exception caugh at (2) In Event View I can see:

Faulting application name: rayguntest.exe, version: 1.0.0.0, time stamp: 0x56a0edc9
Faulting module name: mrt100_app.dll, version: 1.0.23406.0, time stamp: 0x561408ce
Exception code: 0x80000003
Fault offset: 0x000000000000a0ad
Faulting process id: 0x305c
Faulting application start time: 0x01d1545a0fea5649
Faulting application path: C:\Projects\rayguntest\rayguntest\bin\x64\Release\AppX\rayguntest.exe
Faulting module path: C:\Program Files\WindowsApps\Microsoft.NET.Native.Runtime.1.1_1.1.23406.0_x64__8wekyb3d8bbwe\mrt100_app.dll
Report Id: 52bbeeb5-97c6-4814-b5dc-51ee6c3fa9bd
Faulting package full name: 6ca59c51-ed22-482b-acf6-12d241079f4d_1.0.0.0_x64__1d8r4kqm7qz2y
Faulting package-relative application ID: App

We have completed our investigation and this is indeed a bug inside of .NET Native. The issue is that for some cases we didn’t properly handle all cases involving invalid casts. Specifically casting Arrays to a generic type with more than one generic parameter. You can see the spots in Raygun where we are going to run into issues by examining SimpleJson.SerializeValue: https://github.com/MindscapeHQ/raygun4net/blob/67c4bb9fd660afb91d62e9333d75a36a85ee5d4f/Mindscape.Raygun4Net/SimpleJson.cs#L1016

One workaround would be to avoid having this code path serialize an Array in the first place. Another, would be to patch RayGun to check for the array case first and avoid all of the other guesswork it’s trying to do.

The reason you don't see an exception is because the runtime is pretty defensive about the various asserts and fall troughs so it calls the OS FailFast in these cases.

Hope that helps.