Restrict route to controller namespace in ASP.NET Core

Update:

I've found solution through using ActionConstraint. You have to add custom Action Constraint attribute about duplicate actions.

Example with duplicate Index methods.

First HomeController

namespace WebApplication.Controllers
{
    public class HomeController : Controller
    {
        [NamespaceConstraint]
        public IActionResult Index()
        {
            return View();
        }
    }
}

Second HomeController

namespace WebApplication
{
    public class HomeController : Controller
    {
        [NamespaceConstraint]
        public IActionResult Index()
        {
            return View();
        }
    }
}

Configure routing

app.UseMvc(cR =>
   cR.MapRoute("default", "{controller}/{action}", null, null, 
   new { Namespace = "WebApplication.Controllers.HomeController" }));

Action constraint

namespace WebApplication
{
    public class NamespaceConstraint : ActionMethodSelectorAttribute
    {
        public override bool IsValidForRequest(RouteContext routeContext, ActionDescriptor action)
        {
            var dataTokenNamespace = (string)routeContext.RouteData.DataTokens.FirstOrDefault(dt => dt.Key == "Namespace").Value;
            var actionNamespace = ((ControllerActionDescriptor)action).MethodInfo.DeclaringType.FullName;

            return dataTokenNamespace == actionNamespace;
        }
    }
}

First answer:

Does attribute routing funk up the routes defined by app.UseMvc()?

Attribute routing and Convention-based routing (routes.MapRoute(...) work independently. And attribute routes have advantage over convention routes.

but it doesn't seem to do what I want. Is there a way to restrict the routing engine to a certain namespace?

Answer from developers:

Instead of using a list of namespaces to group your controllers we recommend using Areas. You can attribute your controllers (regardless of which assembly they are in) with a specific Area and then create a route for that Area.

You can see a test website that shows an example of using Areas in MVC 6 here: https://github.com/aspnet/Mvc/tree/dev/test/WebSites/RoutingWebSite.

Example using Area with convention-based routing

Controller:

//Reached through /admin/users
//have to be located into: project_root/Areas/Admin/
[Area("Admin")]
public class UsersController : Controller
{

}

Configure convention-based routing:

 app.UseMvc(routes =>
 {
         routes.MapRoute(
         "areaRoute",
         "{area:exists}/{controller}/{action}",
         new { controller = "Home", action = "Index" });
 }

Example using Area with attribute-based routing

//Reached through /admin/users
//have to be located into: project_root/Areas/Admin/
[Area("Admin")]
[Route("[area]/[controller]/[action]", Name = "[area]_[controller]_[action]")]
public class UsersController : Controller
{
    
}