How to test WinUI 3 app different languages?

[pale escarp]

How would I test my WinUI 3 app in different languages including right-to-left languages without changing my system language?

[peak garnet]

You could add a feature to your app that allows you to change only the app's language, however you'll need a library for that, there's one I saw called WinUI3Localizer

[halcyon aspen]

Winuicommunity templates as an add extension in vs code has a great localization of strings .

public static class DynamicLocalizerHelper
{
private static string StringsFolderPath { get; set; } = string.Empty;

public static async Task InitializeLocalizer(params string[] languages)
{
    // Initialize a "Strings" folder in the "LocalFolder" for the packaged app.
    if (PackageHelper.IsPackaged)
    {
        // Create string resources file from app resources if doesn't exists.
        StorageFolder localFolder = ApplicationData.Current.LocalFolder;
        StorageFolder stringsFolder = await localFolder.CreateFolderAsync(
            "Strings",
            CreationCollisionOption.OpenIfExists);
        string resourceFileName = "Resources.resw";
        foreach (var item in languages)
        {
            await LocalizerBuilder.CreateStringResourceFileIfNotExists(stringsFolder, item, resourceFileName);
        }

        StringsFolderPath = stringsFolder.Path;
    }
    else
    {
        // Initialize a "Strings" folder in the executables folder.
        StringsFolderPath = Path.Combine(AppContext.BaseDirectory, "Strings");
        var stringsFolder = await StorageFolder.GetFolderFromPathAsync(StringsFolderPath);
    }

    ILocalizer localizer = await new LocalizerBuilder()
        .AddStringResourcesFolderForLanguageDictionaries(StringsFolderPath)
        .SetOptions(options =>
        {
            options.DefaultLanguage = "en-US";
        })
        .Build();
}

}

Call this in your app.xaml.cs

await DynamicLocalizerHelper.InitializeLocalizer("en-US");