[asp.net-mvc] Set Culture in an ASP.Net MVC app

What is the best place to set the Culture/UI Culture in an ASP.net MVC app

Currently I have a CultureController class which looks like this:

public class CultureController : Controller
{
    public ActionResult SetSpanishCulture()
    {
        HttpContext.Session["culture"] = "es-ES";
        return RedirectToAction("Index", "Home");
    }

    public ActionResult SetFrenchCulture()
    {
        HttpContext.Session["culture"] = "fr-FR";
        return RedirectToAction("Index", "Home");
    }
}

and a hyperlink for each language on the homepage with a link such as this:

<li><%= Html.ActionLink("French", "SetFrenchCulture", "Culture")%></li>
<li><%= Html.ActionLink("Spanish", "SetSpanishCulture", "Culture")%></li>

which works fine but I am thinking there is a more appropriate way to do this.

I am reading the Culture using the following ActionFilter http://www.iansuttle.com/blog/post/ASPNET-MVC-Action-Filter-for-Localized-Sites.aspx. I am a bit of an MVC noob so am not confident I am setting this in the correct place. I don't want to do it at the web.config level, it has to be based on a user's choice. I also don't want to check their http-headers to get the culture from their browser settings.

Edit:

Just to be clear - I am not trying to decide whether to use session or not. I am happy with that bit. What I am trying to work out is if it is best to do this in a Culture controller that has an action method for each Culture to be set, or is there is a better place in the MVC pipeline to do this?

protected void Application_AcquireRequestState(object sender, EventArgs e)
        {
            if(Context.Session!= null)
            Thread.CurrentThread.CurrentCulture =
                    Thread.CurrentThread.CurrentUICulture = (Context.Session["culture"] ?? (Context.Session["culture"] = new CultureInfo("pt-BR"))) as CultureInfo;
        }

Being as it is a setting that is stored per-user, the session is an appropriate place to store the informtion.

I would change your controller to take the culture string as a parameter, rather than having a different action method for each potential culture. Adding a link to the page is easy, and you shouldn't need to write the same code repeatedly any time a new culture is required.

public class CultureController : Controller    
{
        public ActionResult SetCulture(string culture)
        {
            HttpContext.Session["culture"] = culture
            return RedirectToAction("Index", "Home");
        }        
}

<li><%= Html.ActionLink("French", "SetCulture", new {controller = "Culture", culture = "fr-FR"})%></li>
<li><%= Html.ActionLink("Spanish", "SetCulture", new {controller = "Culture", culture = "es-ES"})%></li>

I would do it in the Initialize event of the controller like this...

    protected override void Initialize(System.Web.Routing.RequestContext requestContext)
    {
        base.Initialize(requestContext);

        const string culture = "en-US";
        CultureInfo ci = CultureInfo.GetCultureInfo(culture);

        Thread.CurrentThread.CurrentCulture = ci;
        Thread.CurrentThread.CurrentUICulture = ci;
    }

1: Create a custom attribute and override method like this:

public class CultureAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
    // Retreive culture from GET
    string currentCulture = filterContext.HttpContext.Request.QueryString["culture"];

    // Also, you can retreive culture from Cookie like this :
    //string currentCulture = filterContext.HttpContext.Request.Cookies["cookie"].Value;

    // Set culture
    Thread.CurrentThread.CurrentCulture = new CultureInfo(currentCulture);
    Thread.CurrentThread.CurrentUICulture = CultureInfo.CreateSpecificCulture(currentCulture);
    }
}

2: In App_Start, find FilterConfig.cs, add this attribute. (this works for WHOLE application)

public class FilterConfig
{
    public static void RegisterGlobalFilters(GlobalFilterCollection filters)
    {
    // Add custom attribute here
    filters.Add(new CultureAttribute());
    }
}    

That's it !

If you want to define culture for each controller/action in stead of whole application, you can use this attribute like this:

[Culture]
public class StudentsController : Controller
{
}

Or:

[Culture]
public ActionResult Index()
{
    return View();
}

I know this is an old question, but if you really would like to have this working with your ModelBinder (in respect to DefaultModelBinder.ResourceClassKey = "MyResource"; as well as the resources indicated in the data annotations of the viewmodel classes), the controller or even an ActionFilter is too late to set the culture.

The culture could be set in Application_AcquireRequestState, for example:

protected void Application_AcquireRequestState(object sender, EventArgs e)
    {
        // For example a cookie, but better extract it from the url
        string culture = HttpContext.Current.Request.Cookies["culture"].Value;

        Thread.CurrentThread.CurrentCulture = CultureInfo.GetCultureInfo(culture);
        Thread.CurrentThread.CurrentUICulture = CultureInfo.GetCultureInfo(culture);
    }

EDIT

Actually there is a better way using a custom routehandler which sets the culture according to the url, perfectly described by Alex Adamyan on his blog.

All there is to do is to override the GetHttpHandler method and set the culture there.

public class MultiCultureMvcRouteHandler : MvcRouteHandler
{
    protected override IHttpHandler GetHttpHandler(RequestContext requestContext)
    {
        // get culture from route data
        var culture = requestContext.RouteData.Values["culture"].ToString();
        var ci = new CultureInfo(culture);
        Thread.CurrentThread.CurrentUICulture = ci;
        Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture(ci.Name);
        return base.GetHttpHandler(requestContext);
    }
}

What is the best place is your question. The best place is inside the Controller.Initialize method. MSDN writes that it is called after the constructor and before the action method. In contrary of overriding OnActionExecuting, placing your code in the Initialize method allow you to benefit of having all custom data annotation and attribute on your classes and on your properties to be localized.

For example, my localization logic come from an class that is injected to my custom controller. I have access to this object since Initialize is called after the constructor. I can do the Thread's culture assignation and not having every error message displayed correctly.

 public BaseController(IRunningContext runningContext){/*...*/}

 protected override void Initialize(RequestContext requestContext)
 {
     base.Initialize(requestContext);
     var culture = runningContext.GetCulture();
     Thread.CurrentThread.CurrentUICulture = culture;
     Thread.CurrentThread.CurrentCulture = culture;
 }

Even if your logic is not inside a class like the example I provided, you have access to the RequestContext which allow you to have the URL and HttpContext and the RouteData which you can do basically any parsing possible.

If using Subdomains, for example like "pt.mydomain.com" to set portuguese for example, using Application_AcquireRequestState won't work, because it's not called on subsequent cache requests.

To solve this, I suggest an implementation like this:

1. Add the VaryByCustom parameter to the OutPutCache like this:

   [OutputCache(Duration = 10000, VaryByCustom = "lang")]
   public ActionResult Contact()
   {
       return View("Contact");
   }
   

2. In global.asax.cs, get the culture from the host using a function call:

   protected void Application_AcquireRequestState(object sender, EventArgs e)
   {
       System.Threading.Thread.CurrentThread.CurrentUICulture = GetCultureFromHost();
   }
   

3. Add the GetCultureFromHost function to global.asax.cs:

   private CultureInfo GetCultureFromHost()
   {
       CultureInfo ci = new CultureInfo("en-US"); // en-US
       string host = Request.Url.Host.ToLower();
       if (host.Equals("mydomain.com"))
       {
           ci = new CultureInfo("en-US");
       }
       else if (host.StartsWith("pt."))
       {
           ci = new CultureInfo("pt");
       }
       else if (host.StartsWith("de."))
       {
           ci = new CultureInfo("de");
       }
       else if (host.StartsWith("da."))
       {
           ci = new CultureInfo("da");
       }
   
       return ci;
   }
   

4. And finally override the GetVaryByCustomString(...) to also use this function:

   public override string GetVaryByCustomString(HttpContext context, string value)
   {
       if (value.ToLower() == "lang")
       {
           CultureInfo ci = GetCultureFromHost();
           return ci.Name;
       }
       return base.GetVaryByCustomString(context, value);
   }
   

The function Application_AcquireRequestState is called on non-cached calls, which allows the content to get generated and cached. GetVaryByCustomString is called on cached calls to check if the content is available in cache, and in this case we examine the incoming host domain value, again, instead of relying on just the current culture info, which could have changed for the new request (because we are using subdomains).