ASP.NET Core 3.1 MVC returning AmbiguousMatchException, server error 500

Question

I'm using ASP.NET Core 3.1 MVC and areas.

This problem occurs in development using IIS Express, I haven't even got it to the point I can deploy to a live (IIS) server yet. The server is throwing an error 500 at the end of the startup process.

Exception:

Microsoft.AspNetCore.Routing.Matching.AmbiguousMatchException: The request matched multiple endpoints.

Matches:

FleetLogix.Intranet.Areas.Maps.Controllers.HomeController.Index (FleetLogix.Intranet)
FleetLogix.Intranet.Areas.Admin.Controllers.HomeController.Index (FleetLogix.Intranet)
FleetLogix.Intranet.Controllers.HomeController.Index (FleetLogix.Intranet)

at Microsoft.AspNetCore.Routing.Matching.DefaultEndpointSelector.ReportAmbiguity(CandidateState[] candidateState)
at Microsoft.AspNetCore.Routing.Matching.DefaultEndpointSelector.ProcessFinalCandidates(HttpContext httpContext, CandidateState[] candidateState)
at Microsoft.AspNetCore.Routing.Matching.DefaultEndpointSelector.Select(HttpContext httpContext, CandidateState[] candidateState)
at Microsoft.AspNetCore.Routing.Matching.DfaMatcher.MatchAsync(HttpContext httpContext)
at Microsoft.AspNetCore.Routing.Matching.DataSourceDependentMatcher.MatchAsync(HttpContext httpContext)
at Microsoft.AspNetCore.Routing.EndpointRoutingMiddleware.Invoke(HttpContext httpContext)
at Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.HttpsPolicy.HttpsRedirectionMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

This is my routing:

app.UseEndpoints(endpoints =>
{
    endpoints.MapAreaControllerRoute(
        name: "AdminArea",
        areaName: "Admin",
        pattern: "Admin/{controller=Home}/{action=Index}/{id?}");

    endpoints.MapAreaControllerRoute(
        name: "AnchorArea",
        areaName: "Anchor",
        pattern: "Anchor/{controller=Home}/{action=Index}/{id?}");

    endpoints.MapAreaControllerRoute(
        name: "DashboardArea",
        areaName: "Dashboard",
        pattern: "Dashboard/{controller=DriverBehaviour}/{action=Index}/{id?}");

    endpoints.MapAreaControllerRoute(
        name: "MapsArea",
        areaName: "Maps",
        pattern: "Maps/{controller=Home}/{action=Index}/{id?}");

    endpoints.MapAreaControllerRoute(
        name: "ReportGroupsArea",
        areaName: "ReportGroups",
        pattern: "ReportGroups/{controller=Home}/{action=Index}/{id?}");

    endpoints.MapAreaControllerRoute(
        name: "MaintenanceArea",
        areaName: "Maintenance",
        pattern: "Maintenance/{controller=Home}/{action=Index}/{id?}");

    endpoints.MapControllers();
    endpoints.MapRazorPages();

    endpoints.MapControllerRoute(
        name: "default",
        pattern: "{controller=Home}/{action=Index}/{id?}");
});

I'm not doing anything special. I've seen fixes that say to add an attribute to the methods eg:

[HttpGet("{id:int}")]

but this is complaining about base index methods that have the same profile. The path to them is what's meant to differentiate.

How do I fix this?

user_13655939 · Answer

The path "/" or "/Home/Index" request matched multiple endpoints. You could add area attribute to separate. All tested and worked.

Add [Area("Admin")] to /Area/Admin/HomeController:

  [Area("Admin")]
  public class HomeController : Controller
  {
       public IActionResult Index()
       {
           return View();
       }
  }

Add [Area("Maps")] to /Area/Maps/HomeController

 [Area("Maps")]
 public class HomeController : Controller
 {
     public IActionResult Index()
     {
         return View();
     }
 }

Now you have these mappings:

localhost:44388/admin => /Area/Admin/HomeController/Index Action
localhost:44388/maps => /Area/Maps/HomeController/Index Action
localhost:44388/ => /HomeController/Index Action

ASP.NET Core 3.1 MVC returning AmbiguousMatchException, server error 500

1 Answers