Identity UI no longer works after switching to .net core 3 endpoint routing

Question

After having a hard time getting my area to show with endpoint routing i managed to fix it in this self answered thread (albeit not in a very satisfactory way) : Issue after migrating from 2.2 to 3.0, default works but can't access area, is there anyway to debug the endpoint resolution?

However Identity UI doesn't show at all for me, i get redirected on challenge to the proper url but the page is blank. I have the identity UI nugget package added and, changing from mvc routing to endpoint routing, i didn't change anything that should break it.

I also don't seem to do much different than what the default project does and identity works there even if i add a route as i did in my hack.

As often the issue hides around the line and not on it i'm posting my whole startup file.

Regular (default) controllers work. Admin area works (one of the page doesn't have authentication and i can access it) Any other Admin area page redirect me to /Identity/Account/Login?ReturnUrl=%2Fback (expected behavior) but that page as well as any other /Identity page i tested is blank with no error while running in debug and with a debugger attached.

Any help is most appreciated, full startup bellow:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using FranceMontgolfieres.Models;
using Microsoft.AspNetCore.Mvc.Infrastructure;
using Microsoft.Extensions.Hosting;
using Microsoft.AspNetCore.Diagnostics.HealthChecks;

namespace FranceMontgolfieres
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddSingleton<IConfiguration>(Configuration);

            services
                .Configure<CookiePolicyOptions>(options =>
                {
                    // This lambda determines whether user consent for non-essential cookies is needed for a given request.
                    options.CheckConsentNeeded = context => true;
                    options.MinimumSameSitePolicy = SameSiteMode.None;
                });

            services
                .AddDbContext<FMContext>(options => options
                    .UseLazyLoadingProxies(true)
                    .UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

            services
                .AddDefaultIdentity<IdentityUser>()
                .AddRoles<IdentityRole>()
                .AddEntityFrameworkStores<FMContext>();

            services
                .AddMemoryCache();

            services.AddDistributedSqlServerCache(options =>
            {
                options.ConnectionString = Configuration.GetConnectionString("SessionConnection");
                options.SchemaName = "dbo";
                options.TableName = "SessionCache";
            });

            services.AddHttpContextAccessor();

            services
                .AddSession(options => options.IdleTimeout = TimeSpan.FromMinutes(30));

            services.AddControllersWithViews();
            services.AddRazorPages();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
                app.UseDatabaseErrorPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }

            app.UseHttpsRedirection();
            app.UseRouting();
            app.UseStaticFiles();
            app.UseCookiePolicy();
            app.UseAuthentication();
            app.UseAuthorization();
            app.UseSession(); 

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapAreaControllerRoute("Back", "Back", "back/{controller=Home}/{action=Index}/{id?}");
                endpoints.MapControllerRoute("default","{controller=Home}/{action=Index}/{id?}");
            });
        }

        private async Task CreateRoles(IServiceProvider serviceProvider)
        {
            //initializing custom roles 
            var RoleManager = serviceProvider.GetRequiredService<RoleManager<IdentityRole>>();
            string[] roleNames = { "Admin", "Manager", "Member" };
            IdentityResult roleResult;

            foreach (var roleName in roleNames)
            {
                roleResult = await RoleManager.CreateAsync(new IdentityRole(roleName));
            }
        }
    }
}

Answer 1

The Identity UI is implemented using Razor Pages. For endpoint-routing to map these, add a call to MapRazorPages in your UseEndpoints callback:

app.UseEndpoints(endpoints =>
{
    // ...
    endpoints.MapRazorPages();
});