ASP .NET Core default language is always English

Question

I set the localization as described in Microsoft's blog, but the default language is always English. This is how my Startup.cs looks like with regards to the localization.

CultureInfo[] supportedCultures = new[]
            {
                new CultureInfo("ar"),
                new CultureInfo("en") 
            };

In ConfigureServices method:

services.Configure<RequestLocalizationOptions>(options =>
    {
        options.DefaultRequestCulture = new RequestCulture("ar", "ar");
        options.SupportedCultures = supportedCultures;
        options.SupportedUICultures = supportedCultures;
    });
    services.AddLocalization(options =>
    {
        options.ResourcesPath = "Resources";
    });

    
    services.AddMvc()
    .AddViewLocalization()
    .AddDataAnnotationsLocalization();

In Configure method:

app.UseRequestLocalization(new RequestLocalizationOptions()
{
    DefaultRequestCulture = new RequestCulture("ar"),
    SupportedCultures = supportedCultures,
    SupportedUICultures = supportedCultures
});

Ecclesia

You are setting "arabic" as DefaultRequestCulture but DefaultRequestCulture is used if none of the providers(QueryStringRequestCultureProvider, CookieRequestCultureProvider, AcceptLanguageHeaderRequestCultureProvider) can determine the request culture. My guess is that your browser is set to "english". – Fuel

Interesting, thank you for your insight. Is there a way to override it? – Ecclesia

You can remove QueryStringRequestCultureProvider from RequestCultureProviders – Fuel

Thank you very much, add it as an answer and I will accept it. – Ecclesia

In my case it was due to the fact that I used e.g. "de-DE" or "en-US" instead of e.g. "de" or "en" for the supported cultures and RequestCulture. After the change to e.g. "de" or "en", the system worked perfectly, even if my browser sent e.g. a "de-DE", it was correctly matched with the server-side provided "de" culture/language. – Biauriculate

Answer 1

You are setting "arabic" as DefaultRequestCulture but DefaultRequestCulture is used if none of the built-in providers can determine the request culture. The default providers are:

1. QueryStringRequestCultureProvider
2. CookieRequestCultureProvider
3. AcceptLanguageHeaderRequestCultureProvider

Most likely the culture is determined from the Accept-Language HTTP header that the browser is sending.

You have to remove the AcceptLanguageHeaderRequestCultureProvider in order to fallback to DefaultRequestCulture. To do that, we can overwrite the RequestCultureProviders list of RequestLocalizationOptions and use only the other two providers. In Startup.cs:

public void ConfigureServices(IServiceCollection services)
{
    CultureInfo[] supportedCultures = new[]
    {
        new CultureInfo("ar"),
        new CultureInfo("en")
    };

    services.Configure<RequestLocalizationOptions>(options =>
    {
        options.DefaultRequestCulture = new RequestCulture("ar");
        options.SupportedCultures = supportedCultures;
        options.SupportedUICultures = supportedCultures;
        options.RequestCultureProviders = new List<IRequestCultureProvider>
        {
            new QueryStringRequestCultureProvider(),
            new CookieRequestCultureProvider()
        };
    });
}

and in Configure method just use app.UseRequestLocalization(); before app.UseMvc();

Fuel

Great answer thank you. One more thing - shouldn't it be: var localizationOptions = app.ApplicationServices.GetService<IOptions<RequestLocalizationOptions>>(); app.UseRequestLocalization(localizationOptions.Value); instead of: app.UseRequestLocalization(); in Configure method? – Silverside

Great answer, AcceptLanguageHeaderRequestCultureProvider was taking the localization from the browser headers. – Thacher

Answer 2

If you are using Ajax call to set the culture and respond the back to the client with JSON result.

You have to set the cookie value corresponded to ASP.Net as below in browser level. otherwise, localizer is unable to find the correct culture with cookie value.

var date = new Date();
date.setTime(date.getTime() + (30*24*60*60*1000));
expires = "; expires=" + date.toUTCString();
document.cookie = '.AspNetCore.Culture' + "=c=" + (data.message || "ko-KR") + "|uic=" +(data.message || "ko-KR")  + expires + "; path=/";
window.location.reload();

Elli