在MVC4中更改运行时的路由

Question

Currently when I enter /ru/ it will change to Russian language but then if I go to / it will display Russian resources (meaning cookie/locale is set), however it won't redirect to /ru/ . I can't really just redirect it since, for example if user is on /en/item/32 and he changes language to Russian he needs to be redirected to /ru/item/32 , not /ru .

My [Localization] data-annotation function that checks cookies

public class Localization : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        if (filterContext.RouteData.Values["lang"] != null && !string.IsNullOrWhiteSpace(filterContext.RouteData.Values["lang"].ToString()))
        {
            // Set from route data
            var lang = filterContext.RouteData.Values["lang"].ToString();
            Thread.CurrentThread.CurrentUICulture = CultureInfo.CreateSpecificCulture(lang);
        }
        else
        {
            // Set from cookie
            var cookie = filterContext.HttpContext.Request.Cookies["lang"];
            var langHeader = string.Empty;
            if (cookie != null)
            {
                langHeader = cookie.Value;
                Thread.CurrentThread.CurrentUICulture = CultureInfo.CreateSpecificCulture(langHeader);
            }
            else
            {
                // Cookie does not exist, set default
                Thread.CurrentThread.CurrentUICulture = new CultureInfo("en-US");
            }

            filterContext.RouteData.Values["lang"] = langHeader;
        }

        // Update cookie
        HttpCookie _cookie = new HttpCookie("lang", Thread.CurrentThread.CurrentUICulture.Name);
        _cookie.Expires = DateTime.Now.AddYears(1);
        filterContext.HttpContext.Response.SetCookie(_cookie);
        base.OnActionExecuting(filterContext);
    }
}

And my routes are configured like so

public class RouteConfig
{
    public static void RegisterRoutes(RouteCollection routes)
    {
        routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

        routes.MapRoute(
            name: "Localization",
            url: "{lang}/{controller}/{action}/{id}",
            defaults: new { lang = "en", controller = "Home", action = "Index", id = UrlParameter.Optional },
            namespaces: new string[] { "ORMebeles.Controllers" }
        );

        /*
        routes.MapRoute(
            name: "Default",
            url: "{controller}/{action}/{id}",
            defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional },
            namespaces: new string[] { "ORMebeles.Controllers" }
        );
        */
    }
}

So how can I just inject the {lang} attribute to route and make it stick there?

Answer 1

The trouble you've got here is that OnActionExecuting runs after the incoming request has been evaluated against your routes. So setting filterContext.RouteData.Values["lang"] = langHeader; has no effect in this scenario.

There's a good (MVC 2) example here of how to set up a multi-language site, although this example does not use a lang variable in the url - about halfway down they set up ActionLinks to an action that changes the culture and then redirects back to the previous page.

If you need to keep the lang variable in the URL, you could set up the links to point at the current page, but change the lang parameter, using an HtmlHelper like this:

public static MvcHtmlString ChangeLanguageLink(this HtmlHelper html, string text, string lang)
{
    var currentController = html.ViewContext.RouteData.GetRequiredString("controller");
    var currentAction = html.ViewContext.RouteData.GetRequiredString("action");

    return html.ActionLink(text, currentAction, currentController, new { lang }, null);
}

This should use your route to produce a link that sends the user to the same action but with a different lang - and your Localization filter can set the current culture accordingly.

If there is no lang specified in the url and you need to redirect, then you can set the filterContxt.Result to a RedirectResult with similar parameters as described above.