.NET Core MVC RequestLocalization ignoring DefaultRequestCulture - localization

Question

I've implemented RequestLocalization for es-ES with a single MVC view via the following (note: this code is condensed to only the most relevant pieces):
Startup.cs
public void ConfigureServices(IServiceCollection services)
{
services.AddViewLocalization(LanguageViewLocationExpanderFormat.Suffix,
opts =>
{
opts.ResourcesPath = "Resources";
});
}
public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
var english = "en-US";
var englishRequestCulture = new RequestCulture(culture: english, uiCulture: english);
var supportedCultures = new List<CultureInfo>
{
new CultureInfo("en-US"),
new CultureInfo("es-ES")
};
var options = new RequestLocalizationOptions
{
DefaultRequestCulture = englishRequestCulture,
SupportedCultures = supportedCultures,
SupportedUICultures = supportedCultures
};
app.UseRequestLocalization(options);
app.UseMvc();
}
When passing culture=en-US or culture=es-ES as query string parameters, this works perfectly. My expectation is that the default culture should be en-US when no culture is provided. However, when I do not provide the culture parameter, my view is defaulting to es-ES. I have confirmed that all other Localization providers are also defaulted to en-US.
I should also note that I attempted Localization via ConfigureServices() but was unable to get this to function at all:
services.Configure<RequestLocalizationOptions>(
options =>
{
var supportedCultures = new List<CultureInfo>
{
new CultureInfo("en-US"),
new CultureInfo("es-ES")
};
options.DefaultRequestCulture = new RequestCulture(culture: "en-US", uiCulture: "en-US");
options.SupportedCultures = supportedCultures;
options.SupportedUICultures = supportedCultures;
});

Answer 1

I had the same problem myself. Take a look at your HTTP requests! Do they contain an Accept-Language header set to es-ES (or anything)? Then your localization middleware is working just fine. One of the three default RequestCultureProviders, namely AcceptLanguageHeaderRequestCultureProvider, tries to determine the culture by doing what you did - looking for the Accept-Language header.
So no, the localization middleware does not ignore DefaultRequestCulture, as you and a previous answer suggested.

Answer 2

After much trial and error, I determined that setting the DefaultRequestCulture property has no impact and, as a result, CookieRequestCultureProvider is actually defaulting to es-ES (though I am not entirely sure why, the machine this is running on is set to English and US locale).
As a workaround I modified my existing Configure() method to remove other (currently unused) providers:
private void ConfigureApplicationLocalization(IApplicationBuilder app)
{
var english = "en-US";
var englishRequestCulture = new RequestCulture(culture: english, uiCulture: english);
var supportedCultures = new List<CultureInfo>
{
new CultureInfo("en-US"),
new CultureInfo("es-ES")
};
var options = new RequestLocalizationOptions
{
DefaultRequestCulture = englishRequestCulture,
SupportedCultures = supportedCultures,
SupportedUICultures = supportedCultures
};
//RequestCultureProvider requestProvider = options.RequestCultureProviders.OfType<AcceptLanguageHeaderRequestCultureProvider>().First();
//requestProvider.Options.DefaultRequestCulture = englishRequestCulture;
RequestCultureProvider requestProvider = options.RequestCultureProviders.OfType<CookieRequestCultureProvider>().First();
options.RequestCultureProviders.Remove(requestProvider);
app.UseRequestLocalization(options);
}

Answer 3

I had a similar problem to this. I was translating to Ukrainian language and I was using the country code ua instead of uk.
I changed that and it worked straight away.
Not saying this will fix the OP's problem but hopefully will help someone who comes across this question who has a similar problem.
Full list of codes here:
https://msdn.microsoft.com/en-gb/library/ee825488(v=cs.20).aspx