Unexpected Url.Action output

[Muchiachio]

Given routing in beta5:

app.UseMvc(routes =>
{
    routes.MapRoute(
        name: "DefaultDouble",
        template: "{custom}/{controller}/{action}/{id?}",
        defaults: new { controller = "Home", action = "Index" },
        constraints: new { custom = "Double" });

    routes.MapRoute(
        name: "DefaultSingle",
        template: "{controller}/{action}/{id?}",
        defaults: new { custom = "Single", controller = "Home", action = "Index" },
        constraints: new { custom = "Single" });
});

And calling this from NotHome controller view

@Url.Action("Index", new { custom = "Double" })

results in

/Double

while expected output is

/Double/NotHome

[dougbu]

@Muchiachio is there a typo in your sample? If not where would "NotHome" come from?

[Muchiachio]

No, I just didn't want to write "Broken" in the issue 😄
I updated the sample to keep consistency.

[dougbu]

@Muchiachio my point was the controller value defaults to "Home" in both routes. No route will choose the other controller.

[Muchiachio]

Hmm, but you didn't need to specify other controllers in MVC5 routing, right?

@Url.Action("Index", new { custom = "Double" })

would mean, form an url for current controller and area + add custom route value/query parameter?
So if I am currently in "NotHome" controller's view, Url.Action for index should still be generated for "NotHome" controller? It seems like you need to re-specify current route values then forming an url action.

@Url.Action("Index", new { controller = ViewContext.RouteData.Values["controller"], custom = "Double" })

[rynowak]

Hmm, but you didn't need to specify other controllers in MVC5 routing, right?

That depends on the current value of custom. Both old and new routing codebases have a feature that invalidates route-values when a route-value to the left (lexically, in the template) has a new value.

Ex: - using route:

routes.MapRoute(
        name: "DefaultDouble",
        template: "{custom}/{controller}/{action}/{id?}",
        defaults: new { controller = "Home", action = "Index" });

Current Values: { custom = "Double", controller = "NotHome", action = "Index" }
@Url.Action("Index", "Home", new { custom = "Double" }) should generate /Double/NotHome/Index

In this case, the current (or 'ambient') value of controller is valid, because custom has not changed.

Current Values: { custom = "Single", controller = "NotHome", action = "Index" }
@Url.Action("Index", new { custom = "Double" }) should generate /Double

In this case, the current (or 'ambient') value of controller is not valid, because custom has changed.

[Muchiachio]

Does that mean that there are changes in routing in MVC6?
Because this works just fine in MVC5.

[Eilon]

The same routing logic should be in MVC5 and MVC6 with respect to this...

[rynowak]

The only intended behavior difference between MVC 5 and MVC 6 is that MVC 6 won't generate a link to something that doesn't exist. I'll take a look at the samples.

[rynowak]

I can confirm that this is behaving differently on MVC6. Currently trying to root cause why. Thanks for the report and the helpful repos 👍

[rynowak]

Found the issue here. There's a piece of code in UrlHelper in MVC5 that will explicitly add the ambient values for action and controller to the 'specified values' dictionary.

http://aspnetwebstack.codeplex.com/SourceControl/latest#src/System.Web.Mvc/RouteValuesHelpers.cs

In effect, if you call Url.Action(...) - you're never subject to route-value-invalidation for the 'typical' MVC route tokens of action and controller. area doesn't have any special behavior in this regard.

[Eilon]

Ah yes I vaguely recall that.

[rynowak]

7aa5967