PrimaryLanguageOverride always return null/empty

[ghost1372]

Describe the bug

Microsoft.Windows.Globalization.ApplicationLanguages.PrimaryLanguageOverride is not persisted across app relaunch (unlike UWP behavior).

ApplicationLanguages.PrimaryLanguageOverride behaves differently in WinUI 3 compared to UWP (Windows.Globalization).

In UWP, once PrimaryLanguageOverride is set and the app is relaunched, the value is persisted and can be read again.
In WinUI 3, after relaunching the application, PrimaryLanguageOverride always returns null or an empty string, even though it was previously set successfully.

This creates a behavior inconsistency between UWP and WinUI and makes it impossible to rely on PrimaryLanguageOverride for persistent language selection.

Is this behavior by design, or is it a bug / missing implementation in Microsoft.Windows.Globalization?

If by design, documentation should explicitly state that PrimaryLanguageOverride is not persisted in WinUI 3.

Sorry guys for tagging you:
@stefansjfw
@kmahone
@riverar

Steps to reproduce the bug

1.Create a WinUI 3 desktop application.
2.Set the language override:
Microsoft.Windows.Globalization.ApplicationLanguages.PrimaryLanguageOverride = "en-US";
3.Close the application.
4.Relaunch the application.
5.Read:

Debug.WriteLine(Microsoft.Windows.Globalization.ApplicationLanguages.PrimaryLanguageOverride);

Expected behavior

After relaunch, PrimaryLanguageOverride should still return the previously set value (same behavior as UWP Windows.Globalization.ApplicationLanguages.PrimaryLanguageOverride).

Screenshots

No response

NuGet package version

Latest
None

Packaging type

Packaged
No response

Windows version

11 Latest
No response

IDE

VS2026
No response

Additional context

No response

[hoshiizumiya]

@ghost1372 In my app, it properly works. And it's a packaged app. I think it won't work when it's set as unpackaged mode.
code reference

update:
Ok, I also find that it will return empty when I use

#include <winrt/Microsoft.Windows.Globalization.h>
Microsoft::Windows::Globalization::ApplicationLanguages::PrimaryLanguageOverride()

And it's also packaged situation. but Windows::Globalization::ApplicationLanguages::PrimaryLanguageOverride() is corrent.

[ghost1372]

@hoshiizumiya can you test this sample?

App6.zip

Left side is Microsoft.Windows.Globalization api, and right side is uwp api.

1.First Click on Read Value (it is null)
2.Second Click on Set Value (set language to fa-IR)
3.Third Click on Read Value again (you can see value set successfully)
4.Restart App
5.Click on Read Value again!
6.you can see that value is null/empty.

now you can test steps with right side and see how it is working fine.

[hoshiizumiya]

@ghost1372 Yes, it's just like what you describe.

[ghost1372]

Thank you @hoshiizumiya
I dont know this is by design or it is a bug? mybe @Scottj1s or @DrusTheAxe can clarify.

[hoshiizumiya]

@ghost1372 It definitely is a bug, and maybe you should open an issue in microsoft ui xaml repo. I remember I also meet it before, so I change it to windows sdk api. https://learn.microsoft.com/zh-cn/windows/windows-app-sdk/api/winrt/microsoft.windows.globalization.applicationlanguages.primarylanguageoverride