Q:

set current culture to browser culture by default with ASPNETCore 1.1.1 localisation

I would like to know how to set current culture to browser culture by default with ASPNETCore 1.1.1
I follow this example 
https://andrewlock.net/adding-localisation-to-an-asp-net-core-application/
In my startup.cs I have this
public void ConfigureServices(IServiceCollection services)
{
    services.AddSingleton<IStringLocalizerFactory, SingleFileResourceManagerStringLocalizerFactory>();
    services.AddLocalization(opts => { opts.ResourcesPath = "Resources"; });

    // Add framework services.
    services.AddMvc()
        .AddViewLocalization(
            LanguageViewLocationExpanderFormat.Suffix,
            opts => { opts.ResourcesPath = "Resources"; })
        .AddDataAnnotationsLocalization();

    services.Configure<RequestLocalizationOptions>(
        opts =>
        {
            var supportedCultures = new List<CultureInfo>
            {
                new CultureInfo("en"),
                new CultureInfo("es"),
                new CultureInfo("fr"),
            };

            opts.DefaultRequestCulture = new RequestCulture("fr");
            // Formatting numbers, dates, etc.
            opts.SupportedCultures = supportedCultures;
            // UI strings that we have localized.
            opts.SupportedUICultures = supportedCultures;
        });
}

And I have a language selector, where I add CookieRequestCultureProvider.DefaultCookieName in the cache.
        [HttpPost]
        public IActionResult SetLanguage(string culture, string returnUrl)
        {
                Response.Cookies.Append(
                CookieRequestCultureProvider.DefaultCookieName,
                CookieRequestCultureProvider.MakeCookieValue(new RequestCulture(culture)),
                new CookieOptions { Expires = DateTimeOffset.UtcNow.AddYears(1) }
            );

            return LocalRedirect(returnUrl);
        }

And this resources files

Resources.resx
Resources.en.resx
Resources.es.resx
Resources.fr.resx

This all works fine, the problem here is, each time I call the web site I want to get the default Culture, in this case "fr", but I get always the last one, I choose before I close the web page.
How can I prevent this happen.
Best regards.
Jolynice

A:

Cookies don't die when the user leaves the website, so because you set the cookie's expiration to be in a year, that last language chosen by the user will be in effect for a year.
Unlike cookies, sessions die when the user leaves the website and someone with the same requirement has already requested that feature on github and created a NuGet package for it.
https://github.com/aspnet/Localization/issues/344
https://www.nuget.org/packages/My.AspNetCore.Localization.Session
Other ways around the issue would be to use a shorter expiration date (if you don't need to be very precise) or to delete the cookie when you detect that the user has created a new session.

