Get all routes, including default routes specified at start up

Get_All_Routes_in_ASP.NET_MVC_Core_2.cs

using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc.Abstractions;
using Microsoft.AspNetCore.Mvc.Controllers;
using Microsoft.AspNetCore.Mvc.Infrastructure;
using Microsoft.AspNetCore.Mvc.Internal;
using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.DependencyInjection;
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace Extensions {
    public static class GetAllRoutes {
        public static IApplicationBuilder AllRoutes( this IRouteBuilder routeBuilder, PathString pathString ) {
            var app = routeBuilder.ApplicationBuilder;
            app.Map( pathString, builder => {
                builder.UseMiddleware<GetRoutes>( routeBuilder );
            } );
            return app;
        }

        public static List<T> GetCustomAttributes<T>( this ActionDescriptor actionDescriptor ) where T : Attribute {
            var controllerActionDescriptor = actionDescriptor as ControllerActionDescriptor;
            if ( controllerActionDescriptor != null ) {
                return controllerActionDescriptor.MethodInfo.ReflectedType.GetCustomAttributes( typeof( T ), true ).Select( a => (T)a ).ToList();
            }
            return new List<T>();
        }
    }

    public class GetRoutes {
        private IRouteBuilder _routeBuilder;

        public GetRoutes( RequestDelegate next, IRouteBuilder routeBuilder ) {
            _routeBuilder = routeBuilder;
        }


        public async Task Invoke( HttpContext context ) {
            try {
                var globals = _routeBuilder?.Routes?.Where( r => r.GetType() != typeof( AttributeRoute ) ).Select( r => {
                    Route _r = ( (Route)( r ) );
                    return new {
                        _r.Name,
                        Template = _r.RouteTemplate,
                        DefaultAction = _r.Defaults["action"],
                        DefaultController = _r.Defaults["controller"],
                    };
                } );

                IActionDescriptorCollectionProvider _actionDescriptorCollectionProvider = context.RequestServices.GetRequiredService<IActionDescriptorCollectionProvider>();

                var actions = _actionDescriptorCollectionProvider.ActionDescriptors.Items.Select( a => new {
                    Action = a.RouteValues["action"],
                    Controller = a.RouteValues["controller"],
                    Name = a?.AttributeRouteInfo?.Name,
                    Templates = new string[] { a?.AttributeRouteInfo?.Template },
                    HttpMethods = a?.ActionConstraints?.OfType<HttpMethodActionConstraint>().FirstOrDefault()?.HttpMethods,
                    Authorized = a?.GetCustomAttributes<AuthorizeAttribute>().Any()
                } );

                context.Response.ContentType = "text/json";

                await context.Response.WriteAsync( JsonConvert.SerializeObject( new { globals, actions }, Formatting.Indented ) );
                return;
            } catch ( Exception e ) {
                await context.Response.WriteAsync( $"{e.Message}" );
                return;
            }
        }
    }
}