ASP.NET Core introspect the app's registered routes.

gistfile1.txt

        // in Startup.cs
        
        using Microsoft.AspNetCore.Mvc.Infrastructure;
        using IdentityServer4.Hosting;
        
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            using (var scope = app.ApplicationServices.CreateScope())
            {
                var _obj = scope.ServiceProvider.GetRequiredService<IActionDescriptorCollectionProvider>();
                var _obj1 = _obj.ActionDescriptors.Items;
                // get the app's registered routes.

                var _obj2 = scope.ServiceProvider.GetRequiredService<IEnumerable<Endpoint>>();
                // get the IdentityServer's registered WebAPI endpoints.
                // but there are probably also some RazorPages or MVC pages registered somewhere else,
                // need to find them.
            }
            
            // continues with the usual stuff ...