無法使用 EF Core 播種數據庫

Question

我正在重新創建我的 MVC asp.net 內核，但這次我使用的是 ASP.NET Identity，因為它內置了寄存器/登錄。

我注意到的唯一區別是數據庫是 startup.cs 文件中的“默認連接”，但我不確定為什么這會改變您為數據庫設置種子的方式。 當我運行該項目時，我沒有收到任何構建錯誤或異常，但數據庫沒有播種，並且當我在運行 web 應用程序時嘗試單擊某些內容時出現 404 錯誤。

這正是我的文件在我的其他 ASP.NET 核心項目中的外觀，並且它工作正常，所以我不知道這里有什么問題。 如果有人可以幫助我，我將不勝感激。 謝謝！

這是我的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);

        }
    }
}

我讀到最后一行（SeedData.Initialize）應該為數據庫播種，但我收到一條錯誤消息：

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

所以我暫時把它注釋掉了。

程序.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 （在模型文件夾中）

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; }
    }
}

我使用兩個教程作為參考：

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

實際上，您只需刪除Program.cs中的代碼：

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

然后重新運行您的項目並檢查數據庫。

Answer 2

您在ConfigureServices方法中注冊ApplicationDbContext兩次：

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

嘗試刪除范圍注冊並檢查它是否解決了問題。