How to display correct resource language base on culture in .NET Core - Web API?

Question

I have an issue with language resource is not display correct value base on the culture, I have no problem with ASP.NET Core Web Application, however in the Web API it's not working correctly.

Library => .NET Core 3.1 - Class Library

Language.resx and Language.vi.resx

Web API => .NET Core 3.1

The localization middleware is enabled in the Startup.Configure method as below:

Then in controller, I'm have an action to get the current culture and the value of the resource, however it's always return the value of English

https://localhost:5051/api/home/test?culture=en-US

https://localhost:5051/api/home/test?culture=vi-VN

Answer 1

You need to configure localization in ASP.Net Core Web API a little bit different.

Frist of all, the main issue with folder naming and controller. You need to have the same resource naming and controller. More about in Microsoft documentation. Also, resource folder should be in the same project of ASP.Net Core Web API.

For example: HomeController and Resources/Controllers.HomeController.en-US.resx or Resources/Controllers/HomeController.en-US.resx

I have created new ASP.Net Core Web API project and do the following steps:

1. In ConfigureServices() add this code:

services.AddLocalization(options => options.ResourcesPath = "Resources");
services.Configure<RequestLocalizationOptions>(options => 
{
    var supportedCulters = new List<CultureInfo>()
    {
        new CultureInfo("en-US"),
        new CultureInfo("fr-FR")
    };

    options.DefaultRequestCulture = new RequestCulture(supportedCulters.FirstOrDefault());
    options.SupportedCultures = supportedCulters;
    options.SupportedUICultures = supportedCulters;
});

2. In Configure() add this code:

var requestLocalizationOptions = app.ApplicationServices.GetRequiredService<IOptions<RequestLocalizationOptions>>();
app.UseRequestLocalization(requestLocalizationOptions.Value);

3. Create new resources Resources/Controllers/HomeController.en-US.resx and Resources/Controllers/HomeController.fr-FR.resx
4. Add the following code in HomeController:

private readonly IStringLocalizer<HomeController> _localizer;
public HomeController(IStringLocalizer<HomeController> localizer)
{
    _localizer = localizer;
}

[HttpGet]
public ActionResult Get()
{
    var currentLanguage = CultureInfo.CurrentCulture;
    var result = $"{currentLanguage}-{_localizer["Hello"].Value}";
    return Ok(result);
}

Finally, it works correct.

English text

France text

Solution for Localized Resource in Separate Assembly

Do the following steps:

1. Create empty class Language in folder Resources in your seperate project.
2. Create Language.en-US.resx and Language.fr-FR.resx

3. Inject in HomeController following code

private readonly IStringLocalizer<Language> _localizer;
public HomeController(IStringLocalizer<Language> localizer)
{
    _localizer = localizer;
}

Finally, it works correct for separate assembly project.