ASP.NET Core Attribute Routing - Locale Prefix

Question

I have the following controller:

[Route("blog")]
[Route("{locale:regex(^(de|es|fr)$)}/blog", Order = -1)]
public class BlogController : Controller {
    [HttpGet("{id:int}.htm")]
    [HttpGet("{slug}/{id:int}.htm")]
    public IActionResult Details(string? slug, int id) {
        return View();
    }
}

Now if I try to generate the following URLs:

• @Url.Action("Details", "Blog", new { id = 1 })
• @Url.Action("Details", "Blog", new { slug = "cat-1", id = 1 })
• @Url.Action("Details", "Blog", new { id = 1, locale = "fr" })
• @Url.Action("Details", "Blog", new { slug = "cat-1", id = 1, locale = "fr" })

I would expect the following:

• /blog/1.htm
• /blog/cat-1/1.htm
• /fr/blog/1.htm
• /fr/blog/cat-1/1.htm

However this returns:

• /blog/1.htm
• /blog/1.htm?slug=cat-1
• /fr/blog/1.htm
• /fr/blog/1.htm?slug=cat-1

I have tried changing the order on all the routing attributes but I cannot get it to return the desired result and I’d appreciate any help.

Answer 1

The following example gives the intended results:

public class BlogController : Controller
{
    [Route("{locale:regex(^(de|es|fr)$)}/blog/{slug}/{id:int}.htm")]
    [Route("{locale:regex(^(de|es|fr)$)}/blog/{id:int}.htm", Order = 1)]
    [Route("blog/{slug}/{id:int}.htm", Order = 2)]
    [Route("blog/{id:int}.htm", Order = 3)]
    public IActionResult Details(string? slug, int id)
    {
        return View();
    }
}

This approach uses an earlier Order for more specific routes, so that those are checked first. The obvious downside is the verbosity, but it's a working solution based on the requirements described.