MVC 5 culture and redirect query string loses value

Question

this seems like any other question about culture or routing, but I can't figure out why this is happening.

When I try to access an [Authorize] element without being authenticated, I'm redirected to login page with a ReturnUrl param in query string. That's perfect. (boilerplate app)

Now my problem is: if I do the same with localisation within url (from routeConfig) ie: url: "{lang}/{controller}/{action}", I'm being redirected a first time with this parameter, but after been passed by the base controller that redirect me to a localized route. After that, ReturnUrl is null while login page (.cshtml) is loaded...

I've loooked into lots of articles, and tried numerous tricks/options and maybe on the way I did something that's breaks everything, so here are some code:

First RouteConfig :

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

    routes.MapRoute(
       name: "LocalizedDefault",
       url: "{lang}/{controller}/{action}",
       defaults: new { lang = UrlParameter.Optional, controller = "Home", action = "Index" } ,
       constraints: new { lang = "fr-CA|en-US" }
   );

    routes.MapRoute(
       name: "Default",
       url: "{controller}/{action}/{id}",
       defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
   );

}

In BaseController:

protected override IAsyncResult BeginExecuteCore(AsyncCallback callback, object state)
{
    string cultureName = RouteData.Values["lang"] as string;
    // Attempt to read the culture cookie from Request
    if (cultureName == null)
    {
        cultureName = Request.UserLanguages != null && 
        Request.UserLanguages.Length > 0 ? 
                            Request.UserLanguages[0] :
                            null; // obtain it from HTTP header AcceptLanguages
    }

    // Validate culture name
    cultureName = CultureHelper.GetImplementedCulture(StartupMVC.SupportedLangs, cultureName);

    if (RouteData.Values["lang"] as string != cultureName)
    {
        // Force a valid culture in the URL
        RouteData.Values["lang"] = cultureName.ToLowerInvariant(); // lower case too 

        // Redirect user
        //Response.SuppressFormsAuthenticationRedirect = false;

****HERE**** 
if I comment this line, I keep returnUrl but my route 
is like {controller}/{action}/{id} => So default language   
    Response.RedirectToRoute(RouteData.Values);  
otherwise route ok {lang}/{controller}/{action}/{id} but no ReturnUrl

    }                                                                                
    SetCurrentCultureOnThread(cultureName);
    return base.BeginExecuteCore(callback, state);
}

and a bit of Login.cshtml:

@using (Html.BeginForm("Login", "Account", new { ReturnUrl = ViewBag.ReturnUrl }, FormMethod.Post, new { @class = "form-horizontal", role = "form" }))
{
        ... 
}

I hope this is silly and there is some obvious solution you could point out to me. Otherwise, does anyone understand this? and maybe help me to fix it?

PS : if I not being clear enough or you need some more info, please comment what you need! :)

Edit : from NightOwl888's comment, I'd like to add some more questions:

_I kwow there is at least 3 major ways of handling localization (locale in query string, in route, translating the url), but is there any documented or commonly used Best Practices regarding localization and culture?

_How does the .NET framework handles the redirect to login and how does it handles the query string? (since we can not register route with query string values)

Too many problems with this approach to list here. See [ASP.NET MVC 5 culture in route and url](https://stackoverflow.com/a/32839796) and be sure to read the comments about redirecting the user automatically to their culture. — NightOwl888, Feb 17 '18 at 07:08
thanks for this comment. I saw this answer, and I thought it was somewhat complicated for something that nowadays must widely be used... Since you seem to know a lot on that subject, and I'm curious to know more, I'll add on my question some additional questions, as it might be valuable for other people. — Minus, Feb 19 '18 at 14:50
There is nothing built-in to MVC to make it skip over the localized route and go to the non-localized one (without resorting to 302 redirects). In fact, there are no built-in extensions for URL localization at all - the only choices are to customize or go 3rd party. However, I can't stress enough how bad it is to let the request go all the way to a controller and then redirect to another controller. Redirecting has **one** purpose - to change the URL in the browser. Routing's purpose is to make the *first* request go directly to the right controller, eliminating the need for a second request. — NightOwl888, Feb 20 '18 at 08:02
BTW - the above link is my highest voted answer on SO. It didn't get to be that way because it is too complicated for people to implement. It is literally 2 classes to copy, paste and configure plus a little bit of modification to a view to allow the user to switch cultures. The attribute routing code is only required if you need to localize attribute routes. — NightOwl888, Feb 20 '18 at 08:24

score 3 · Answer 1 · answered Jun 03 '18 at 10:55

Added QueryStrings to end of Routes:

if (cultureOnUrl.ToLower() != culture.ToLower())
        {
            try
            {
                var routes = new RouteValueDictionary(filterContext.RouteData.Values);
                foreach (string key in filterContext.HttpContext.Request.QueryString.Keys)
                {
                    routes[key] = filterContext.HttpContext.Request.QueryString[key];
                }
                if (!routes.ContainsKey("lang"))
                    routes.Add("lang", culture);
                else
                    routes["lang"] = culture;  
           filterContext.HttpContext.Response.RedirectToRoute("LocalizedDefault",routes);     
            }
            catch (Exception ex)
            {

            }
            return;
        }

score 1 · Answer 2 · answered Feb 16 '18 at 22:58

1

Specifically tell MVC which route to use. So instead of this:

Response.RedirectToRoute(RouteData.Values);

do this:

Response.RedirectToRoute("LocalizedDefault", RouteData.Values);

answered Feb 16 '18 at 22:58

CodingYoshi

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@Minus Be more specific please. What does not work? Do you get an error? – CodingYoshi Feb 19 '18 at 14:21
I ment using the name of the route (in my case 'LocalizedDefault' ) does not correct the problem as the returnUrl still got to null after beeing redirected to that route. – Minus Feb 19 '18 at 14:42
@Minus What values do you have in `RouteData.Values`? Please check in the debugger before you make the redirect. – CodingYoshi Feb 19 '18 at 14:43
In RouteData.Values before the call to rediretToRoute are : Account, Login, and en-US. – Minus Feb 19 '18 at 14:55
1

@Minus that is the issue. You need to do this before you call the redirect: `RouteData.Values.Add("returnUrl", "whatever...");` – CodingYoshi Feb 19 '18 at 15:09
RouteData Values are different that query string values. If I understand correctly how routes works, what you're suggesting implies adding a "Verb" in my route. So instead of "{lang}/{controller}/{action}/{id}", I would have a url like "{lang}/{controller}/{action}/{id}/{ReturnUrl}"? This might conflicts with other routes as the applications grows? – Minus Feb 19 '18 at 15:33
@Minus No you do not need to add a verb in your route. Whatever is not in your route table will be treated as query string. Please try it. – CodingYoshi Feb 19 '18 at 15:35
That works! nice... Could you maybe explain a bit more how this works (see Edit in question and comment from @NightOwl888)? – Minus Feb 19 '18 at 15:58

MVC 5 culture and redirect query string loses value

2 Answers2