发生异常时，Developer Exception Page为空白

Question

我已经阅读了很多关于这个问题的帖子，我仍然无法找到我的应用程序中出现此问题的原因。环境设置为开发，程序执行行app.UseDeveloperExceptionPage();。这是代码。

Startup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using TheWorld.Services;
using Microsoft.Extensions.Configuration;
using TheWorld.Models;
using Newtonsoft.Json.Serialization;
using AutoMapper;
using TheWorld.ViewModels;

namespace TheWorld
{
    public class Startup
    {
        private IHostingEnvironment _env;
        private IConfigurationRoot _config;

        public Startup(IHostingEnvironment env)
        {
            _env = env;

            var builder = new ConfigurationBuilder()
                .SetBasePath(_env.ContentRootPath)
                .AddJsonFile("config.json")
                .AddEnvironmentVariables();

            _config = builder.Build();
        }

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddSingleton(_config);

            if (_env.IsEnvironment("Development") || _env.IsEnvironment("Testing"))
            {
                services.AddScoped<IMailService, DebugMailService>();
            }
            else
            {
                // Implement real Mail Service
            }

            services.AddMvc()
                .AddJsonOptions(config =>
                {
                    config.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();
                });

            services.AddLogging();

            services.AddDbContext<WorldContext>();

            services.AddScoped<IWorldRepository, WorldRepository>();

            services.AddTransient<GeoCoordsService>();

            services.AddTransient<WorldContextSeedData>();

        }

        public void Configure(IApplicationBuilder app, 
            IHostingEnvironment env, 
            ILoggerFactory loggerFactory,
            WorldContextSeedData seeder,
            ILoggerFactory factory)
        {
            if (env.IsEnvironment("Development"))
            {
                app.UseDeveloperExceptionPage();
                factory.AddDebug(LogLevel.Information);
            }
            else
            {
                factory.AddDebug(LogLevel.Error);
            }

            app.UseStaticFiles();

            Mapper.Initialize(config =>
            {
                config.CreateMap<TripViewModel, Trip>().ReverseMap();
                config.CreateMap<StopViewModel, Stop>().ReverseMap();
            });

            app.UseMvc(config =>
            {
                config.MapRoute(
                    name: "Default",
                    template: "{controller}/{action}/{id?}",
                    defaults: new { controller = "App", action = "Index" }
                );
            });

            seeder.EnsureSeedData().Wait();
        }
    }
}

project.json

{
  "dependencies": {
    "Microsoft.NETCore.App": {
      "version": "1.0.1",
      "type": "platform"
    },
    "Microsoft.AspNetCore.Diagnostics": "1.0.0",
    "Microsoft.AspNetCore.Server.IISIntegration": "1.0.0",
    "Microsoft.AspNetCore.Server.Kestrel": "1.0.1",
    "Microsoft.Extensions.Logging.Console": "1.0.0",
    "Microsoft.AspNetCore.StaticFiles": "1.0.0",
    "Microsoft.AspNetCore.Mvc": "1.0.1",
    "Microsoft.AspNetCore.Mvc.TagHelpers": "1.0.1",
    "Microsoft.Extensions.Configuration.Json": "1.0.0",
    "Microsoft.EntityFrameworkCore": "1.0.1",
    "Microsoft.EntityFrameworkCore.Tools": {
      "version": "1.0.0-preview2-final",
      "type": "build"
    },
    "Microsoft.EntityFrameworkCore.SqlServer": "1.0.1",
    "AutoMapper": "4.2.1",
    "Microsoft.AspNetCore.Authorization": "1.0.0",
    "Microsoft.Extensions.Logging.Debug": "1.0.0"
  },

  "tools": {
    "Microsoft.AspNetCore.Server.IISIntegration.Tools": "1.0.0-preview2-final",
    "Microsoft.EntityFrameworkCore.Tools": {
      "version": "1.0.0-preview2-final",
      "imports": [
        "portable-net45+win8+dnxcore50",
        "portable-net45+in8"
      ]
    }
  },

  "frameworks": {
    "netcoreapp1.0": {
      "imports": [
        "dotnet5.6",
        "portable-net45+win8"
      ]
    }
  },

  "buildOptions": {
    "emitEntryPoint": true,
    "preserveCompilationContext": true
  },

  "runtimeOptions": {
    "configProperties": {
      "System.GC.Server": true
    }
  },

  "publishOptions": {
    "include": [
      "wwwroot",
      "web.config"
    ]
  },

  "scripts": {
    "postpublish": [ "dotnet publish-iis --publish-folder %publish:OutputPath% --framework %publish:FullTargetFramework%" ]
  }
}