.NET Core 5运行时错误：默认启动配置文件无法应用及JSON反序列化失败

问题背景 #

我正在学习一门.NET Core课程，在EF模块中发现课程作者拼接了不同时期的录制内容，代码未经演示就发生变更，最终我陷入困境不知如何推进，恳请帮助。

操作步骤与错误信息 #

我运行了以下命令：

PS I:\Users\Ron\Projects\MVC\DutchTreat> dotnet run /seed

得到错误：

The launch profile "(Default)" could not be applied.
A usable launch profile could not be located.
Unhandled exception. System.Text.Json.JsonException: The JSON value could not be converted to System.Collections.Generic.IEnumerable`1[DutchTreat.Data.Entities.Product]. Path: $ | LineNumber: 0 | BytePositionInLine: 1.
    at System.Text.Json.ThrowHelper.ThrowJsonException_DeserializeUnableToConvertValue(Type propertyType)
    at System.Text.Json.Serialization.Converters.IEnumerableDefaultConverter`2.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, TCollection& value)
    at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
    at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
    at System.Text.Json.JsonSerializer.ReadCore[TValue](JsonConverter jsonConverter, Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
    at System.Text.Json.JsonSerializer.ReadCore[TValue](Utf8JsonReader& reader, Type returnType, JsonSerializerOptions options)
    at System.Text.Json.JsonSerializer.Deserialize[TValue](String json, Type returnType, JsonSerializerOptions options)
    at System.Text.Json.JsonSerializer.Deserialize[TValue](String json, JsonSerializerOptions options)
    at DutchTreat.Data.DutchSeeder.Seed() in I:\Users\Ron\Projects\MVC\DutchTreat\Data\DutchSeeder.cs:line 34
    at DutchTreat.Program.RunSeeding(IHost host) in I:\Users\Ron\Projects\MVC\DutchTreat\Program.cs:line 41
    at DutchTreat.Program.Main(String[] args) in I:\Users\Ron\Projects\MVC\DutchTreat\Program.cs:line 26

相关代码 #

DutchContext.cs #

using DutchTreat.Data.Entities;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Configuration.Ini;
using Microsoft.IdentityModel.Tokens;
using System;

namespace DutchTreat.Data
{
    public class DutchContext : DbContext
    {
        private readonly IConfiguration _config;

        public DutchContext(IConfiguration config)
        {
            _config = config;
        }

        public DbSet<Product> Products { get; set; }
        public DbSet<Order> Orders { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            base.OnConfiguring(optionsBuilder);
            optionsBuilder.UseSqlServer(_config["ConnectionStrings:DutchContextDb"]);
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);

            modelBuilder.Entity<Order>()
                .HasData(new Order()
                {
                    Id=1,
                    OrderDate=DateTime.UtcNow,
                    OrderNumber="12345"
                });
        }
    }
}

DutchSeeder.cs #

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Text.Json;
using System.Threading.Tasks;
using DutchTreat.Data.Entities;
using Microsoft.AspNetCore.Hosting;

namespace DutchTreat.Data
{
    public class DutchSeeder
    {
        private readonly DutchContext _ctx;
        private readonly IWebHostEnvironment _env;

        public DutchSeeder(DutchContext ctx,IWebHostEnvironment env)
        {
            _ctx = ctx;
            _env = env;
        }

        public void Seed()
        {
            _ctx.Database.EnsureCreated();

            if (!_ctx.Products.Any())
            {
                // 生成示例数据
                var filePath = Path.Combine(_env.ContentRootPath,"Data/art.json");
                var json = File.ReadAllText(filePath);
                var products = JsonSerializer.Deserialize<IEnumerable<Product>>(json);

                _ctx.Products.AddRange(products);

                var order = new Order()
                {
                    OrderDate = DateTime.Today,
                    OrderNumber = "10000",
                    Items = new List<OrderItem>()
                    {
                        new OrderItem()
                        {
                            Product=products.First(),
                            Quantity=5,
                            UnitPrice=products.First().Price
                        }
                    }
                };
                _ctx.Orders.Add(order);

                _ctx.SaveChanges();
            }
        }
    }
}

Program.cs #

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using DutchTreat.Data;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.DependencyInjection;
using System.IO;

namespace DutchTreat
{
    public class Program
    {
        public static void Main(string[] args)
        {
            //var host = BuildWebHost(args);
            var host = CreateHostBuilder(args).Build();

            if (args.Length == 1 && args[0].ToLower() =="/seed")
            {
                RunSeeding(host);
                return;
            }

            host.Run();           
        }

        private static void RunSeeding(IHost host)
        {
            var scopeFactory = host.Services.GetService<IServiceScopeFactory>();
            
            using (var scope = scopeFactory.CreateScope())
            { 
                var seeder = scope.ServiceProvider.GetService<DutchSeeder>();
                seeder.Seed();
            }   
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureAppConfiguration(SetupConfiguration)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                });

        private static void AddConfiguration(HostBuilderContext ctx, 
            IConfigurationBuilder bldr)
        {
            bldr.Sources.Clear();

            bldr.SetBasePath(Directory.GetCurrentDirectory())
                .AddJsonFile("config.json")
                .AddEnvironmentVariables();
        }
        private static void SetupConfiguration(HostBuilderContext ctx, IConfigurationBuilder builder)
        {
            // 移除默认配置选项
            builder.Sources.Clear();

            builder.AddJsonFile("config.json", false, true)
                    .AddEnvironmentVariables();
        }
    }
}

Startup.cs #

using DutchTreat.Controllers;
using DutchTreat.Data;
using DutchTreat.Services;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Design;

namespace DutchTreat
{
    public class Startup
    {
        // 运行时会调用此方法，用于向容器添加服务
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddDbContext<DutchContext>();
            services.AddTransient<DutchSeeder>();
            services.AddTransient<IMailService,NullMailService>();

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

        // 运行时会调用此方法，用于配置HTTP请求管道
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            //app.UseDefaultFiles();
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/error");
            }
            app.UseStaticFiles();
            app.UseRouting();
            app.UseEndpoints(cfg =>
                    {
                        cfg.MapRazorPages();
                        cfg.MapControllerRoute("Default",
                                                "/{controller}/{action}/{id?}",
                                                new { controller = "App", action = "Index" });
                    });
        }
    }
}

launchSettings.json #

{
    "profiles": {
        "IIS Express": {
            "commandName": "IISExpress",
            "launchBrowser": true,
            "environmentVariables": {
            "ASPNETCORE_ENVIRONMENT": "Production"
            }
        }
    },
    "iisSettings": {
        "windowsAuthentication": false,
        "anonymousAuthentication": true,
        "iisExpress": {
            "applicationUrl": "http://localhost:8888",
            "sslPort": 0
        }
    }
}

内容的提问来源于stack exchange，提问作者user1372603