Configuring ASP.NET MVC Attribute Routing for multi language site

Question

I'm creating a MVC5 web site that should support multiple languages. The structure of the app is complex so I'm using Attribute Routing only. RouteConfig.cs is very simple:

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

I want to keep language information in URL by adding language identifier after site name. For English, which is default language, URL should remain "clean". Here are an example:

http://test.com/foo/1/bar/2
http://test.com/de/foo/1/bar/2

My first attempt was to use two RoutePrefix attributes for each controller:

[RoutePrefix("foo")]
[RoutePrefix("{lang}/foo")]

But MVC doesn't allow to use more than one RoutePrefix attribute for a controller.

So now I'm not using RoutePrefix attributes at all, and specify full route for each controller action:

[Route("foo/{a}/bar/{b}")]
[Route("{lang}/foo/{a}/bar/{b}")]

Is there any better way to handle lang route? Ideally I would like to specify in one place only, not for every controller.

PS. I'm setting current thread culture by parsing language route in custom filter.

• NightOwl888: Have a look at this answer. For attribute routing, read the comments.
• Aleksandr Ivanov: So your suggestion is just to add two routes for each action? Or I missed something?
• NightOwl888: You could 1) add 2 routes per action 2) use conventional routing or 3) analyze the source for MapMvcAttributeRoutes and make a similar method that registers a localized route for each Route attribute (be sure to call your custom method before MapMvcAttributeRoutes to put the routes into the RouteTable in the right order).
• NightOwl888: I updated my other answer with an example of the 3rd option.
• Aleksandr Ivanov: Have you tried to execute your code for attribute routing? When method MapMvcAttributeRoutes() is called to create a copy of routes, then first route is of type RouteCollectionRoute which can't be casted to Route. And even if I ignore that, these added localized routes are not working.

Answer 1

I found the easiest solution (at least for ASP.NET MVC 5.2) is to use a default value for the optional parameter.

For example, if English is your default language, you can use a single attribute on the Controller:

[RoutePrefix("{lang=en}/foo")]

or a single attribute on the Action:

[Route("{lang=en}/foo/bar")]

Note that optional URI parameters (e.g. {lang?}) don't work if they are at the start of the URL.

Answer 2

If all else fails then I suggest you keep your default routes as is and store the language in a query parameter

For English, your default language, URL will remain "clean" as you intended.

http://test.com/foo/1/bar/2

But for other languages you include lang as query parameter

http://test.com/foo/1/bar/2?lang=De-DE

Then in your custom filter, check if the query parameter is present. If it is then change culture to match. Otherwise use default language.

Also: You should use 5 character encoding and not 2 char globalization ISO code. De-DE and not DE or fr-FR and not FR

• Aleksandr Ivanov: I was thinking about this approach, but I would like to keep URL as clean as possible.

Answer 3

You basically need three things:

• A multi-language aware route to handle incoming URLs (if you're using MVC5 or above you could also go for Attribute-based routing instead, but I still prefer to use a global rule to handle this).
• A LocalizationAttribute to handle these kinds of multi-language requests.
• An helper method to generate these URLs within your application (Html.ActionLink and/or Url.Action extension methods).

See this answer for further details and code samples.

• Code sample for multi-language Html.ActionLink extension
• Code sample for multi-language Url.Action extension

(both are written in C# - affiliation disclaimer: I made those samples)

For additional info and further samples you can also read this blog post I wrote on this topic.

http://www.ryadel.com/en/html-actionlink-extension-method-written-c-handle-multi-language-routes-asp-net-mvc/