如何使用实体框架在 .NET Core 6 中播种数据？

Question

我知道如何使用我的Seeder class 和Seed()方法在startup.cs文件中使用旧的.NET 5.0将数据播种到数据库中，从而创建一些初始数据。

public void Configure(IApplicationBuilder app, IHostingEnvironment env, Seeder seeder)
{
   seeder.Seed();

   ..............
   // other configurations
}

如何在.NET 6.0中执行此操作？ 没有地方可以添加我的Seeder class 作为参数。

Answer 1

我解决了一个类似的问题如下：

程序.cs (.NET 6)

...
builder.Services.AddScoped<IDbInitializer, DbInitializer>(); //can be placed among other "AddScoped" - above: var app = builder.Build();   

...    
SeedDatabase(); //can be placed above app.UseStaticFiles();
...    
    void SeedDatabase() //can be placed at the very bottom under app.Run()
    {
        using (var scope = app.Services.CreateScope())
        {
            var dbInitializer = scope.ServiceProvider.GetRequiredService<IDbInitializer>();
            dbInitializer.Initialize();
        }
    }

Answer 2

我以前从未使用过您的解决方案。 这就是我正在做的，

public class DataContext: DbContext
{
    public DataContext(DbContextOptions options) : base(options)
    {
        
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        new DbInitializer(modelBuilder).Seed();
    }
    
    // Db sets
}

和

public class DbInitializer
{
    private readonly ModelBuilder modelBuilder;

    public DbInitializer(ModelBuilder modelBuilder)
    {
        this.modelBuilder = modelBuilder;
    }

    public void Seed()
    {
        modelBuilder.Entity<User>().HasData(
               new User(){ Id = 1.... },
               new User(){ Id = 2.... },

        );
    }
}

然后运行命令

dotnet ef migrations add .......

创建迁移文件

和

dotnet ef database update

更新数据库

Answer 3

就我而言，我正在使用 Microsoft.AspNetCore.Identity 并需要使用种子方法在数据库中使用默认值初始化应用程序。

builder.Services.AddScoped<UserManager<ApplicationUser>>();
builder.Services.AddScoped<RoleManager<IdentityRole>>();

在包含的行之后

var app = builder.Build();

我已经调用了种子方法：

using (var scope = app.Services.CreateScope())
{
var userManager = scope.ServiceProvider.GetRequiredService<UserManager<Usuario>>();
var roleManager = scope.ServiceProvider.GetRequiredService<RoleManager<IdentityRole>>();
await DefaultRoles.SeedAsync(roleManager);
await DefaultAdmin.SeedAsync(userManager);
}

Answer 4

.NET 6.0

使用这些链接获取详细版本：

• 教程：在 ASP.NET Core MVC web 应用程序中开始使用 EF Core
• AspNetCore.Docs

Program.cs

var builder = WebApplication.CreateBuilder(args);

//Add services to the container.
builder.Services.AddDbContext<YourDbContext>(
    optionsBuilder => optionsBuilder.UseSqlServer("Your connection string goes here") //install - Microsoft.EntityFrameworkCore.SqlServer to use ".UseSqlServer" extension method
builder.Services.AddScoped<DbInitializer>();

var app = builder.Build();

//Configure the HTTP-request pipeline
if (app.Environment.IsDevelopment())
{
    app.UseItToSeedSqlServer();    //custom extension method to seed the DB
    //configure other services
}

app.Run();

DbInitializerExtension.cs

internal static class DbInitializerExtension
{
    public static IApplicationBuilder UseItToSeedSqlServer(this IApplicationBuilder app)
    {
        ArgumentNullException.ThrowIfNull(app, nameof(app));

        using var scope = app.ApplicationServices.CreateScope();
        var services = scope.ServiceProvider;
        try
        {
            var context = services.GetRequiredService<YourDbContext>();
            DbInitializer.Initialize(context);
        }
        catch (Exception ex)
        {

        }

        return app;
    }
}

DbInitializer.cs

internal class DbInitializer
{
    internal static void Initialize(YourDbContext dbContext)
    {
        ArgumentNullException.ThrowIfNull(dbContext, nameof(dbContext));
        dbContext.Database.EnsureCreated();
        if (dbContext.Users.Any()) return;

        var users = new User[]
        {
            new User{ Id = 1, Name = "Bruce Wayne" }
            //add other users
        };

        foreach(var user in users)
            dbContext.Users.Add(user);

        dbContext.SaveChanges();
    }
}