无法使用 EF Core 为数据库播种

Question

我正在重新创建我的 MVC asp.net 核心，但这次我使用 ASP.NET Identity，因为它内置了 register/log-in。

我注意到的唯一区别是数据库是 startup.cs 文件中的“默认连接”，但我不确定为什么这会改变您为数据库设置种子的方式。当我运行项目时，我没有收到任何构建错误或异常，但数据库没有种子，并且当我运行在 Web 应用程序中尝试单击某些内容时出现 404 错误。

这正是我的文件在我的其他 ASP.NET 核心项目中的样子，它工作正常，所以我不知道这里的问题是什么。如果有人可以帮助我，我将不胜感激。谢谢！

这是我的 Startup.cs 文件：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Identity.UI;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.EntityFrameworkCore;
using EasyEats.Data;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using EasyEats.Models;

namespace EasyEats
{
    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.AddDbContext<ApplicationDbContext>(options =>
                options.UseSqlServer(
                    Configuration.GetConnectionString("DefaultConnection")));
            services.AddDefaultIdentity<IdentityUser>(options => options.SignIn.RequireConfirmedAccount = true)
                .AddEntityFrameworkStores<ApplicationDbContext>();
            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.UseStaticFiles();

            app.UseRouting();

            app.UseAuthentication();
            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllerRoute(
                    name: "default",
                    pattern: "{controller=Home}/{action=Index}/{id?}");
                endpoints.MapRazorPages();
            });

            //SeedData.Initialize(app.ApplicationServices);

        }
    }
}

我读到最后一行 (SeedData.Initialize) 应该为数据库设置种子，但我却收到一条错误消息：

"System.InvalidOperationException: 'Cannot resolve scoped service 'Microsoft.EntityFrameworkCore.DbContextOptions`1[EasyEats.Data.ApplicationDbContext]' from root provider.'

所以我暂时把它注释掉了。

Program.cs

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

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


            using (var scope = host.Services.CreateScope())
            {
                var services = scope.ServiceProvider;

                try
                {
                    SeedData.Initialize(services);
                }
                catch (Exception ex)
                {
                    var logger = services.GetRequiredService<ILogger<Program>>();
                    logger.LogError(ex, "An error occurred seeding the DB.");
                }
            }

            host.Run();
        }

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

SeedData.cs（在模型文件夹中）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using EasyEats.Data;

namespace EasyEats.Models
{
    public class SeedData
    {
        public static void Initialize(IServiceProvider serviceProvider)
        {
            using (var context = new ApplicationDbContext(
                serviceProvider.GetRequiredService<
                    DbContextOptions<ApplicationDbContext>>()))
            {
                // Look for any movies.
                if (context.Restaurants.Any())
                {
                    return;   // DB has been seeded
                }

                context.Restaurants.AddRange(
                    new Restaurant
                    {
                        RestaurantName = "McDonalds",
                        RestaurantDescription = "McDonald's Corporation sells hamburgers, chicken sandwiches, French fries, soft drinks, breakfast items, and desserts.",
                    },

                    new Restaurant
                    {
                        RestaurantName = "Burger King",
                        RestaurantDescription = "Burger King Corporation, restaurant company specializing in flame-broiled fast-food hamburgers.",
                    },

                    new Restaurant
                    {
                        RestaurantName = "Chipotle",
                        RestaurantDescription = "Chipotle is a fast-casual chain that's known for its build-your-own burritos, rice bowls, and other Mexican dishes.",
                    },

                    new Restaurant
                    {
                        RestaurantName = "Chick-fil-A",
                        RestaurantDescription = "Chick-fil-A is one of the largest American fast food restaurant chains and the largest whose specialty is chicken sandwiches.",
                    }
                );
                context.SaveChanges();

            }
        }
    }
}

ApplicationDbContext.cs

using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore;
using EasyEats.Models;

namespace EasyEats.Data
{
    public class ApplicationDbContext : IdentityDbContext
    {
        public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
            : base(options)
        {
        }
        public DbSet<Restaurant> Restaurants { get; set; }
        public DbSet<MenuItem> MenuItems { get; set; }
        public DbSet<CartItem> CartItems { get; set; }
    }
}

我正在使用两个教程作为参考：

https://docs.microsoft.com/en-us/aspnet/core/tutorials/first-mvc-app/adding-model?view=aspnetcore-5.0&tabs=visual-studio

https://docs.microsoft.com/en-us/aspnet/identity/overview/getting-started/introduction-to-aspnet-identity

Answer 1

您在 ConfigureServices 方法中注册了您的 ApplicationDbContext 两次：

 services.AddScoped<ApplicationDbContext>();
 services.AddDbContext<ApplicationDbContext>(options =>
                      options.UseSqlServer(
                              Configuration.GetConnectionString("DefaultConnection")));

尝试删除作用域注册并检查它是否解决了问题。

Answer 2

其实你只需要删除你里面的代码Program.cs:

CreateHostBuilder(args).Build().Run();

然后重新运行您的项目并检查数据库。

无法使用 EF Core 为数据库播种

Unable to seed database with EF Core

c#

asp.net-identity

entity-framework-core

asp.net-core