WinAppSDK 1.8: MRM.cpp's MrmGetFilePathFromName now reports error when the resources.pri file doesn't exist

[qiutongMS]

Describe the bug

Depending on calling context, with WinAppSDK version 1.7, this function used to return "resources.pri" from the current exe path even if that file doesn't exist. Now the function checks for existence and returns ERROR_FILE_NOT_FOUND (https://github.com/haonanttt/WindowsAppSDK/blob/main/dev/MRTCore/mrt/Core/src/MRM.cpp#L1085) (which seems to contradict the function's documentation BTW).

So this now can break Microsoft.Windows.ApplicationModel.Resources's ResourceManager https://github.com/haonanttt/WindowsAppSDK/blob/main/dev/MRTCore/mrt/Microsoft.Windows.ApplicationModel.Resources/src/ResourceManager.cpp#L18 in the case this file doesn't exist (which again contradicts ResourceManager 's code comment)

Steps to reproduce the bug

It's in a XAML island (Win32 desktop app hosts .NET + WinUI3 class library) context. There's a full repro project here: https://github.com/smourier/Win32ShowsWinUI3

Uncomment this line to reproduce: https://github.com/smourier/Win32ShowsWinUI3/blob/main/WinUI3ClassLibrary/SampleWindow.xaml.cs#L43

Expected behavior

This should work as before
Maybe there's a workaround

Screenshots

No response

NuGet package version

Windows App SDK 1.8.0: 1.8.250907003

Packaging type

Unpackaged

Windows version

Windows 11 version 24H2 (26100, June 2025 Update)

IDE

Visual Studio 2022

Additional context

No response

[qiutongMS]

I've found a workaround that seems to work in my setup: you need to subscribe to the Application.ResourceManagerRequested event, and offer it a custom ResourceManager instance pointing to the <WinAppSDK_FrameworkPackage>\resources.pri file.

[qiutongMS]

I've found a workaround that seems to work in my setup: you need to subscribe to the Application.ResourceManagerRequested event, and offer it a custom ResourceManager instance pointing to the <WinAppSDK_FrameworkPackage>\resources.pri file.

I'm afraid that your solution might not work as expected if the user really wants WinUI to read their custom resources file(?)

Anyway it's a workaround, and MrmGetFilePathFromName is violating its documents here.

[qiutongMS]

It's probably the same issue yes. Your workaround the regression seems to work, thanks, but is there a simple way to determine the WinAppSDK's current (loaded) runtime's path from .NET?

FWIW, this is how I currently do it (and my repo where the initial link points has now this workaround applied):

    private class DummyApp : Application, IXamlMetadataProvider
    {
        public DummyApp()
        {
            ...
            ResourceManagerRequested += (s, e) =>
            {
                var module = GetModuleHandleW("MRM");
                var sb = new StringBuilder(1024);
                _ = GetModuleFileNameW(module, sb, sb.Capacity);
                var resources = Path.Combine(Path.GetDirectoryName(sb.ToString())!, "resources.pri");
                e.CustomResourceManager = new ResourceManager(resources);
            };
        }

        [DllImport("kernel32", CharSet = CharSet.Unicode)]
        private static extern nint GetModuleHandleW(string lpModuleName);

        [DllImport("kernel32", CharSet = CharSet.Unicode)]
        private static extern int GetModuleFileNameW(nint hModule, StringBuilder lpFilename, int nSize);
    }

[qiutongMS]

You might want to take a look at an example in the official unpackaged apps deployment documentation: https://learn.microsoft.com/en-us/windows/apps/windows-app-sdk/deploy-unpackaged-apps#option-2-deploy-windows-app-sdk-runtime-packages-directly