ASP.NET Core 2.1 MVC localized routing

A route localization example for ASP.NET Core 2.1 MVC. The solution uses attributes on the controllers and actions to determine the localized routes for each different culture. A convention is added in Startup.cs to iterate over all the controllers and actions to set their routes based on the [LocalizationRoute] attributes.

Note: This solution doesn't seem to work with Areas. #Issue 28

Code used for the blog post: https://saaratrix.blogspot.com/2017/12/localized-routing-aspnet-core-mvc-2.html

For the old solution for ASP.NET Core 1.0 MVC release candidate 1

Other solutions:

BrightSoul has done a ASP.NET Core 3.1 version that uses resource files to set up the routing instead of attributes. https://github.com/BrightSoul/aspnetcore-localization-demo

Example usage for a controller:

// Routes for each culture:
// Default: /Home           - / for the Index action
// Finnish: /fi/koti        - /fi for the Index action.
// Swedish: /sv/Hem         - /sv for the Index action.
[LocalizationRoute("fi", "koti")]
[LocalizationRoute("sv", "Hem", "Hemma")] // The link text for <a>linktext</a> will be Hemma
public class HomeController : LocalizationController
{
    public IActionResult Index()
    {
        return View();
    }

    // Routes for each culture:
    // Default: /Home/About
    // Finnish: /fi/koti/meistä
    // Swedish: /sv/Hem/om
    [LocalizationRoute("fi", "meistä")]
    [LocalizationRoute("sv", "om")]
    public IActionResult About()
    {
        return View();
    }
}

And example of using the CultureActionLinkTagHelper in the views for the anchor element.

// Generated html: <a href="/Home/About">About</a>
<a asp-controller="home" asp-action="about" cms-culture="en">About</a>

// Generated html: <a href="/fi/koti/meistä">Meistä</a>
<a asp-controller="home" asp-action="about" cms-culture="fi">About</a>

// Generated html: <a href="/sv/Hem/om">Om</a>
<a asp-controller="home" asp-action="about" cms-culture="sv">About</a>

// Leaving cms-culture="" empty will use the current request culture.
// If user is at /fi/... then finnish culture is used then the generated html would be:
// <a href="/fi/koti/meistä">Meistä</a>
<a asp-controller="home" asp-action="about" cms-culture="">About</a>

To set up the localization you need to include it in Startup.cs or an equivalent file in your project. The method everything is set up in is:
public void ConfigureServices(IServiceCollection services) In this method we set settings such as what the supported cultures are. You could set the DefaultCulture and SupportedCultures directly in the LocalizationRouteDataHandler.cs class as well. Example usage with 3 cultures, en, fi, sv

public void ConfigureServices(IServiceCollection services)
{
        // ... Other code above here ...
        // Set up what culture to use
        LocalizationRouteDataHandler.DefaultCulture = "en";
        LocalizationRouteDataHandler.SupportedCultures = new Dictionary<string, string>()
        {
            { "en", "English" },
            { "fi", "Suomeksi" },
            { "sv", "Svenska" }
        };
        // Add the LocalizationRouteConvention to MVC Conventions.
        // Without this the localized routes won't work because this is what initializes all the routes!
        IMvcBuilder mvcBuilder = services.AddMvc(options =>
        {
            options.Conventions.Add(new LocalizationRouteConvention());
        });
        // Set up the request localization options which is what sets the culture for every http request.
        // Meaning if you visit /controller the culture is LocalizationRouteDataHandler.DefaultCulture.
        // And if you visit /fi/controller the culture is fi.
        services.Configure<RequestLocalizationOptions>(options =>
        {
            options.DefaultRequestCulture = new RequestCulture(LocalizationRouteDataHandler.DefaultCulture, LocalizationRouteDataHandler.DefaultCulture);
            foreach (var kvp in LocalizationRouteDataHandler.SupportedCultures)
            {
                CultureInfo culture = new CultureInfo(kvp.Key);
                options.SupportedCultures.Add(culture);
                options.SupportedUICultures.Add(culture);
            }
            options.RequestCultureProviders = new List<IRequestCultureProvider>()
            {
                new UrlCultureProvider(options.SupportedCultures)
            };
        });
        // Set up Resource file usage and IViewLocalizer
        services.AddLocalization(options => options.ResourcesPath = "Resources");
        // Views.Shared._Layout is for the /Views/Shared/_Layout.cshtml file
        mvcBuilder.AddViewLocalization(LanguageViewLocationExpanderFormat.Suffix)
        // Add support for localizing strings in data annotations (e.g. validation messages) via the
        // IStringLocalizer abstractions.
        .AddDataAnnotationsLocalization();
        // ... Other code below here ...
}

LocalizationDataHandler.cs has the default values used by the localization app. For example if your default controller isn't Home then change it in this file or in Startup.cs depending on your preference.

public static class LocalizationRouteDataHandler
{
    /// <summary>
    /// The default culture.
    /// </summary>
    public static string DefaultCulture { get; set; }
    /// <summary>
    /// The dictionary of all supported cultures.
    /// Key = Culture Name
    /// Value = Display Name
    /// Example: en, English
    /// </summary>
    public static Dictionary<string, string> SupportedCultures { get; set; }
    public static string DefaultController { get; set; } = "Home";
    public static string DefaultAction { get; set; } = "Index";
}

markchipman/asp.net-core-mvc-localized-routing

ASP.NET Core 2.1 MVC localized routing

Other solutions: