Dynamic routing in ASP.NET Core 3.1 when part of the url is already another route

[jsabrooke]

Using the code:

app.UseEndpoints(endpoints =>
{
    var defaults = new { controller = "Home", action = "Index" };
    endpoints.MapControllerRoute(name: "test", pattern: "category/product1", defaults: defaults);
    endpoints.MapDynamicControllerRoute<RouteValueTransformer>("{**slug}");
});

I would expect:

• "category/product2" to attempt to find a route by entering the RouteValueTransformer.TransformAsync method. However, it doesn't, which appears to be because the first part, "category", is matched. It then gives a 404 as there isn't actually a route for it.

If you change "category" to anything else, it will enter the TransformAsync method as expected, which is why I think it's just matching the first "category" part of the url.

I'm not sure if this is expected behaviour, a bug, or if we're using the "pattern" parameter wrong, or maybe {**slug} wrong?

I made a Stack Overflow post for this as well with a bit more detail, but I think the above is enough for here.

https://stackoverflow.com/questions/59971600/dynamic-routing-in-asp-net-core-3-1-when-part-of-the-url-is-already-another-rout

It's a different problem, but maybe the same cause as #16579 ?

Thanks very much!

To Reproduce

It's very easy to reproduce. Create a new ASP.NET Core 3.1 web application using the template in VS 2019. Add the code above to Startup.Configure.

Add

services.AddSingleton<RouteValueTransformer>();

to Startup.ConfigureServices.

Add

public class RouteValueTransformer : DynamicRouteValueTransformer
{
    public override async ValueTask<RouteValueDictionary> TransformAsync(HttpContext httpContext, RouteValueDictionary values)
    {
        return values;
    }
}

Then put a breakpoint on "return values;", and see when it gets hit by different urls.

Further technical details

• ASP.NET Core 3.1.0
• VS 2019 Professional 16.4.3
• Include the output of dotnet --info:

.NET Core SDK (reflecting any global.json):
Version: 3.1.101
Commit: b377529961

Runtime Environment:
OS Name: Windows
OS Version: 10.0.18363
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\3.1.101\

Host (useful for support):
Version: 3.1.1
Commit: a1388f194c

.NET Core SDKs installed:
1.1.14 [C:\Program Files\dotnet\sdk]
2.1.202 [C:\Program Files\dotnet\sdk]
2.1.509 [C:\Program Files\dotnet\sdk]
2.2.100 [C:\Program Files\dotnet\sdk]
2.2.207 [C:\Program Files\dotnet\sdk]
2.2.401 [C:\Program Files\dotnet\sdk]
3.1.100 [C:\Program Files\dotnet\sdk]
3.1.101 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:
Microsoft.AspNetCore.All 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.1.14 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.1.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.2.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.1.14 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.1.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.2.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 1.0.16 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 1.1.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.1.14 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.1.15 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.2.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 3.1.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

[mkArtakMSFT]

Thanks for contacting us, @jsabrooke.
@javiercn can you please look into this? Thanks!

[douwinga]

Ran into this exact issue today too. As a workaround I found that using attribute routing works instead of using MapControllerRoute.

[jsabrooke]

Thanks a lot @douwinga ! I'll try that while waiting for a resolution on this.

[ygoe]

I have no idea what "attribute routing" should look like in this scenario. (Or in mine, see last referenced issue.)

[jsabrooke]

Closing as I've just discovered that it's a duplicate of #18677, which was created about half a day before mine was, and a fix is planned:

https://docs.microsoft.com/en-us/aspnet/core/mvc/controllers/routing?view=aspnetcore-3.1#conventional-routing-order