Conventional routing with custom templates not working when you have area attributes

[davidliang2008]

Is this a Bug or Feature request?:

Bug

Steps to reproduce (preferably a link to a GitHub repo with a repro project):

https://github.com/davidliang2008/DL.Issues.AspNetCore.Mvc.CustomRouting

Description of the problem:

When you want a more user/SEO friendly URLs on your site, you would set up custom routings to use slugs instead of ids.

public void Configure(IApplicationBuilder app, IHostingEnvironmentt env)
{
    ...

    app.UseMvc(routes =>
    {
        routes.MapRoute(
                name: "productListByTypeRoute",
                template: "products/{type}",
                defaults: new { area = "", controller = "products", action = "listByType" }
        );

        routes.MapRoute(
                name: "productListByCategoryRoute",
                template: "products/{type}/{category}",
                defaults: new { area = "", controller = "products", action = "listByCategory" }
        );

        routes.MapRoute(
                name: "productDetailsRoute",
                template: "products/{type}/{category}/{product}",
                defaults: new { area = "", controller = "products", action = "details" }
        );

        routes.MapRoute(
                name: "areaRoute",
                template: "{area:exists}/{controller=dashboard}/{action=index}/{id?}"
        );

        routes.MapRoute(
                name: "default",
                template: "{controller=home}/{action=index}/{id?}");
        );
    });

    ...
}

And then I have the controller and action setup to handle those requests.

public class ProductsController : Controller
{
     ...

    public async Task<IActionResult> ListByType(string type)
    {
        ...
        return View(...);
    }

    public async Task<IActionResult> ListByCategory(string type, string category)
    {
        ...
        return View(...);
    }

    public async Task<IActionResult> Details(string type, string category, string product)
    {
        ...
        return View(...);
    }

    ...
}

So the following links are expected to call their corresponding actions:

Link	Action	Parameters
/products/countertop	ListByType	type=countertop
/products/countertop/2cm-granite	ListByCategory	type=countertop, category=2cm-granite
/products/countertop/2cm-granite/imperial-splendor	Details	type=countertop, category=2cm-granite, product=imperial-splendor

Everything works fine until you add an area! All custom URLs would return 404!

[Area("admin")]
public abstract class AdminControllerBase : Controller {}

public class DashboardController : AdminControllerBase
{
    public IActionResult Index()
    {
        return View();
    }
}

Notes:

1. With the area routing setup in Startup, as long as the [Area("admin")] is commented out, all custom links would work with the setting new { area = "", ... }.
2. If you have [Area("admin")] on, the only way to get those custom links to work is to remove area = "" from custom routing setup.
3. This setup worked flawlessly in previous Microsoft.AspNetCore.Mvc 2.0.7!

Version of Microsoft.AspNetCore.Mvc or Microsoft.AspNetCore.App or Microsoft.AspNetCore.All:

V2.1.0

[kichalla]

@davidliang2008 From the repro app its not clear where you are trying to generate the links from. Are you doing it from the DashboardController to Products? if so, the ambient value of 'admin' is probably being used.

[davidliang2008]

No, all product links are public. They're not under Admin area. I have the ProductController defined just as a regular Controller and 3 more actions within it: ListByType, ListByCategory and Details. For testing purpose, All 3 actions return Index view with different string so that we know which action is getting called.

The issue is:

• The links in the table in the OP work as long as [Area()] is not used.
• If you use any area in the app, admin area being just an example, the links in the table won't work and all return 404.
• The links in the table in the OP work with area being used in the app when you remove area="" in those 3 custom route mapping defaults in Startup.cs, which I don't understand.

Hope I explained it clearly.

[kichalla]

Ah yes, I am able to reproduce the issue. Investigating the cause...

[kichalla]

So seems like the root cause of the issue is change in behavior of the GetHashCode api on StringComparer.

In netcoreapp2.0, the following prints 0:

Console.WriteLine(StringComparer.OrdinalIgnoreCase.GetHashCode(""));   // here "" can be thought as area=""

Since this used to give 0, we have logic of a string being null also as 0

In netcoreapp2.1, the above code prints a non-zero value which causes a look up miss for action descriptors where they are built with key like area=null and the look value is area=""

cc @rynowak

@davidliang2008 as a workaround, you can change your route configuration to be like

defaults: new { area = (string)null, controller = "products", action = "listByType" }

[pranavkm]

FYI @stephentoub in case the behavior change was unintentional.

[davidliang2008]

You guys are awesome!!

[stephentoub]

FYI @stephentoub in case the behavior change was unintentional.

It's intentional. Randomized string hashing was enabled for IgnoreCase in 2.1.

[kichalla]

Places that require changes:
https://github.com/aspnet/Mvc/blob/release/2.2/src/Microsoft.AspNetCore.Mvc.Core/Internal/ActionSelector.cs#L434
https://github.com/aspnet/Routing/blob/master/src/Microsoft.AspNetCore.Routing/RouteValueEqualityComparer.cs#L45

[kichalla]

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