播种一个值对象。最好的方法。带EF核的.NET 6

Question

我有一个实体Product和一个ValueObject Money。

public class Product
{
    public Product() { }
    [Key]
    public int Id { get; set; }
    public string Name { get; set; }    
    public Money Price { get; set; }
}

public class Money : BaseValueObject
{
    public Money(string currency, decimal amount)
    {
        if (string.IsNullOrEmpty(currency)) 
            throw new ArgumentNullException(nameof(currency));

        this.Currency = currency;
        this.Amount   = amount;
    }

    public string Currency { get; private set; }
    public decimal Amount  { get; private set; }

    protected override IEnumerable<object?> GetEqualityComponents()
    {
        yield return Currency;
        yield return Amount;
    }
}

我以这种方式设置了一个表配置：

public class ProductEntityTypeConfiguration : IEntityTypeConfiguration<Product>
{
    public void Configure(EntityTypeBuilder<Product> builder)
    {
        builder.ToTable("Products");
        builder.HasKey(product => product.Id);

        builder.Property(product => product.Name)
               .HasColumnName("Name");

        builder.OwnsOne(product => product.Price,
            navigationBuilder =>
            {
                navigationBuilder.Property(money => money.Amount)
                                 .HasColumnName("Price");
                navigationBuilder.Property(money => money.Currency)
                                 .HasColumnName("Currency");
            });
    }
}

public class ProductContext : DbContext
{
    public ProductContext(DbContextOptions<ProductContext> options) : base(options) { }
    public DbSet<Product> Products { get; set; }

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

        modelBuilder.ApplyConfiguration(new ProductEntityTypeConfiguration());

        // seeding
        modelBuilder.Entity<Product>(p =>
        {
            p.HasData(
                new Product { Id = 1, Name = "cola" },
                new Product { Id = 2, Name = "chips" },
                new Product { Id = 3, Name = "candy" }
            );
            p.OwnsOne(p => p.Price).HasData(
                new Money("EUR", 100),
                new Money("EUR", 050),
                new Money("EUR", 065)
            );
        });
    }

因为Money是一个valueObject，所以它没有键。我希望使用此配置存储在同一个Product中，而不是1个price字段，2个字段:一个名为"Price“，另一个称为”货币“。

配置运行正常，但是当“种子”执行时，我得到：

System.InvalidOperationException：“无法添加实体类型”Money“的种子实体，因为所需的属性”ProductId“没有提供任何价值。”

不明白为什么要ProductId。那么，什么是ValueObject种子的正确方式呢？

我使用的是.NET 6和EF核心6。

Answer 1

对于用于跟踪的拥有实体类型，需要拥有类型的主键作为阴影属性创建。。拥有类型的实例的键的值将与所有者实例的键值相同。

可以使用匿名对象将它的值指定为种子数据：

modelBuilder.Entity<Product>(p =>
{
    p.HasData(
        new Product { Id = 1, Name = "cola" },
        new Product { Id = 2, Name = "chips" },
        new Product { Id = 3, Name = "candy" }
    );
    p.OwnsOne(pr => pr.Price)
        .HasData(
            new { ProductId = 1, Currency = "EUR", Amount = 100m },
            new { ProductId = 2, Currency = "EUR", Amount = 050m },
            new { ProductId = 3, Currency = "EUR", Amount = 065m }
        );
});

Answer 2

作为另一种选择，您可以使用以下方法创建一个静态类：

public class ProductEntityTypeConfiguration : IEntityTypeConfiguration<Product>
{
    public void Configure(EntityTypeBuilder<Product> builder)
    {
        // ...

        builder.OwnsOne(product => product.Price,
            navigationBuilder =>
            {
                // ...
                DataSeeder.Seed(navigationBuilder)
            });

        DataSeeder.Seed(builder);
    }

    private class DataSeeder
    {
        private static readonly List<Product> Products = new()
        {
            new Product { Name = "cola", Price = { Currency = "EUR", Amount = 100m } },
            new Product { Name = "chips", Price = { Currency = "EUR", Amount = 100m } },
            new Product { Name = "candy", Price = { Currency = "EUR", Amount = 100m } }
        }

        public static void Seed(EntityTypeBuilder<Product> builder)
        {
            builder.HasData(Products.Select((p, i) => new
            {
                ProductId = i + 1,
                p.Name,
            }));
        }

        public static void Seed(OwnedNavigationBuilder<Product, Money> builder)
        {
            builder.HasData(Products.Select((p, i) => new
            {
                ProductId = i + 1,
                p.Price.Currency,
                p.Price.Amount,
            }));
        }
    }
}

对于我来说，这似乎更容易读懂，而且您不必显式地指定ids。