使用C＃10，.NET 6和EF Core 6更改嵌套值对象的值的问题

Question

我的汇总是这样的：

public class Order : AggregateRoot
{
    private readonly List<OrderItem> _items = new();

    public DateTime Date { get; set; }
    public IReadOnlyCollection<OrderItem> Items => _items;

    public void SetItemDiscounts(int itemId, IEnumerable<Discount> discounts)
    {
        var orderItem = _items.Single(item => item.Id == itemId);
        orderItem.SetDiscounts(discounts);
    }
}

public class OrderItem : Entity
{
    private readonly List<Discount> _discounts = new();

    public int OrderId { get; private set; }
    public int Qty { get; private set; }
    public Money Price { get; private set; }
    public IReadOnlyCollection<Discount> Discounts => _discounts;

    public void SetDiscounts(IEnumerable<Discount> discounts)
    {
        _discounts.Clear();
        _discounts.AddRange(discounts);
    }
}

public class Discount : ValueObject<Discount>
{
    public int Plan { get; private set; }
    public Money Amount { get; private set; }
}

public class Money : ValueObject<Money>
{
    public int CurrencyId { get; private set; }
    public decimal Value { get; private set; }
}

EF核心的配置是：

protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Order>().HasKey(x => x.Id);
        modelBuilder.Entity<Order>().Property(t => t.Id)
            .HasColumnType(nameof(SqlDbType.BigInt)).IsRequired();
        modelBuilder.Entity<Order>().Property(t => t.Date)
            .HasColumnType(nameof(SqlDbType.DateTime2)).IsRequired();

        modelBuilder.Entity<Order>().HasMany<OrderItem>().WithOne()
            .HasForeignKey(x => x.OrderId);

        modelBuilder.Entity<OrderItem>().HasKey(x => x.Id);
        modelBuilder.Entity<OrderItem>().Property(t => t.Id)
            .HasColumnType(nameof(SqlDbType.Int)).IsRequired();
        modelBuilder.Entity<OrderItem>().Property(t => t.Qty)
            .HasColumnType(nameof(SqlDbType.Int)).IsRequired();

        modelBuilder.Entity<OrderItem>().OwnsOne(x => x.Price)
            .Property(x => x.Value).HasColumnType(nameof(SqlDbType.Decimal))
            .HasColumnName("Price").IsRequired();

        modelBuilder.Entity<OrderItem>().OwnsMany(
            orderItem => orderItem.Discounts,
            discountNavigationBuilder =>
            {
                discountNavigationBuilder.Property(p => p.Plan)
                    .HasColumnType(nameof(SqlDbType.Int)).IsRequired();
                discountNavigationBuilder.OwnsOne(
                    discount => discount.Amount,
                    amountNavigationBuilder =>
                    {
                        amountNavigationBuilder.Property(p => p.CurrencyId)
                            .HasColumnType(nameof(SqlDbType.Int)).HasColumnName("CurrencyId").IsRequired();
                        amountNavigationBuilder.Property(p => p.Value)
                            .HasColumnType(nameof(SqlDbType.Decimal)).HasColumnName("Amount").IsRequired();
                    });
            });
    }

当我创建带有项目和折扣的订单时没有问题，但是当我使用setDiscounts方法更新折扣时，我会遇到此错误：

system.invalidoperationException：属性：属性'Discount.amount＃Money.discountid'是密钥的一部分，因此无法修改或标记为修改。要将现有实体的本金与识别外键更改，请首先删除因子并调用“ savechanges”，然后将依赖人与新的本金相关联。

这里的折扣是什么？我的配置或任何其他代码有什么问题吗？

Answer 1

在EF核心中进行了一些搜索和研究之后，我发现有一个价值对象的功能。我更改了代码，它的工作原理很好：

public class Money : ValueObject<Money>
{
    public enum CurrencyType
    {
        USD = 1,
        IRI = 2
    }

    private Money(decimal value) => Value = value;

    public Money(decimal value, CurrencyType currencyType)
    {
        Value = Math.Round(value, currencyType == CurrencyType.USD ? 2 : 0);
    }

    public decimal Value { get; }

    public static Money Zero => new(0);
    
    public static implicit operator decimal(Money money) => money.Value;
    
    public static Money operator +(decimal a, Money b) => new (a + b.Value);

    public static Money operator +(Money a, decimal b) => new (a.Value + b);
}

我写了一个类的前值转换：

public class MoneyValueConverter : ValueConverter<Money, decimal>
{
    public MoneyValueConverter() : base(
            money => money.Value,
            value => Money.Zero + value
        )
    {
    }
}

我将EF配置更改为：

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Order>().HasKey(x => x.Id);
    modelBuilder.Entity<Order>().Property(t => t.Id)
        .HasColumnType(nameof(SqlDbType.BigInt)).IsRequired();
    modelBuilder.Entity<Order>().Property(t => t.Date)
        .HasColumnType(nameof(SqlDbType.DateTime2)).IsRequired();

    modelBuilder.Entity<Order>().HasMany<OrderItem>().WithOne()
        .HasForeignKey(x => x.OrderId);

    modelBuilder.Entity<OrderItem>().HasKey(x => x.Id);
    modelBuilder.Entity<OrderItem>().Property(t => t.Id)
        .HasColumnType(nameof(SqlDbType.Int)).IsRequired();
    modelBuilder.Entity<OrderItem>().Property(t => t.Qty)
        .HasColumnType(nameof(SqlDbType.Int)).IsRequired();

    modelBuilder.Entity<OrderItem>()
        .Property(t => t.Price)
        .HasConversion<MoneyValueConverter>()
        .HasColumnName(nameof(OrderItem.Price))
        .HasColumnType(nameof(SqlDbType.Decimal))
        .IsRequired();

    modelBuilder.Entity<OrderItem>().OwnsMany(
        orderItem => orderItem.Discounts,
        discountNavigationBuilder =>
        {
            discountNavigationBuilder
                .Property(p => p.Plan)
                .HasColumnType(nameof(SqlDbType.Int))
                .IsRequired();
            discountNavigationBuilder
                .Property(t => t.Amount)
                .HasConversion<MoneyValueConverter>()
                .HasColumnName(nameof(Discount.Amount))
                .HasColumnType(nameof(SqlDbType.Decimal))
                .IsRequired();
        });
}