Entity Framework 核心 2.1 - 自有类型和嵌套值对象

Question

我正在学习 DDD，我目前正在学习的教程是使用 NHibernate 实现的，但由于我缺乏使用它的经验，我决定使用 EF Core 2.1 完成本课程。

但是，我目前有点卡在以下内容中：我有三个 classes Customer，它是一个实体和两个值对象（CustomerStatus 及其内部值对象 ExpirationDate) - 像这样：

public class Customer : Entity
{
    //... constructor, other properties and behavior omitted for the sake of simplicity
    public CustomerStatus Status { get; set; }
}

public class CustomerStatus : ValueObject<CustomerStatus>
{
    // customer status is enum containing two values (Regular,Advanced)
    public CustomerStatusType Type { get; }
    public ExpirationDate ExpirationDate { get; }
}

public class ExpirationDate : ValueObject<ExpirationDate>
{
    //... constructor, other properties and behavior omitted for the sake of simplicity
    public DateTime? Date { get; private set; }
}

当我尝试在 DbContext 中执行以下操作时：

modelBuilder.Entity<Customer>(table =>
{      
   table.OwnsOne(x => x.Status,
     name =>
     {
        name.Property(x => x.ExpirationDate.Date).HasColumnName("StatusExpirationDate");
        name.Property(x => x.Type).HasColumnName("Status");
     });
});

我收到以下错误：

The expression 'x => x.ExpirationDate.Date' is not a valid property expression. The expression should represent a simple property access: 't => t.MyProperty'.
Parameter name: propertyAccessExpression'

除此之外，我还尝试过以下操作：

table.OwnsOne(x => x.Status.ExpirationDate,
      name =>
      {
         name.Property(x => x.Date).HasColumnName("StatusExpirationDate");
      });
 table.OwnsOne(x => x.Status,
      name =>
      {
          name.Property(x => x.Type).HasColumnName("Status");
      });

但这也导致：

The expression 'x => x.Status.ExpirationDate' is not a valid property expression. The expression should represent a simple property access: 't => t.MyProperty'.

我也试过：

modelBuilder.Entity<Customer>()
                    .OwnsOne(p => p.Status, 
              cb => cb.OwnsOne(c => c.ExpirationDate));

但也没有运气......无论如何，我们将不胜感激任何帮助，如果可能的话，如果有人能解释为什么我的 none 尝试不起作用，那将是非常好的？提前致谢！

更新

首先按照 Ivan 的评论中所述进行操作后，我收到有关 CustomerStatus class 构造函数的错误，因此我添加了默认保护的构造函数。

之后我开始收到错误：

Field 'k__BackingField' of entity type 'CustomerStatus' is readonly and so cannot be set.

这是我的CustomerStatusclass的内幕，如果有帮助的话：

public class CustomerStatus : ValueObject<CustomerStatus>
{
    public CustomerStatusType Type { get; }
    public ExpirationDate ExpirationDate { get; }

    public static readonly CustomerStatus Regular =
        new CustomerStatus(CustomerStatusType.Regular, ExpirationDate.Infinite);
    public bool IsAdvanced => Type == CustomerStatusType.Advanced && !ExpirationDate.IsExpired;

    private CustomerStatus(CustomerStatusType type, ExpirationDate expirationDate)
    {
        Type = type;
        ExpirationDate = expirationDate;
    }

    protected CustomerStatus()
    {

    }
    public static CustomerStatus Create(CustomerStatusType type, ExpirationDate expirationDate)
    {
        return new CustomerStatus(type, expirationDate);
    }

    public CustomerStatus Promote()
    {
        return new CustomerStatus(CustomerStatusType.Advanced, ExpirationDate.Create(DateTime.UtcNow.AddYears(1)).Value);
    }

    protected override bool EqualsCore(CustomerStatus other)
    {
        return Type == other.Type && ExpirationDate == other.ExpirationDate;

    }

    protected override int GetHashCodeCore()
    {
        return Type.GetHashCode() ^ ExpirationDate.GetHashCode();
    }
}

更新

它所要做的就是在 CustomerStatus class 内的 Type 和 ExpirationDate 属性上添加私有设置器，并结合 Ivan 的回答，它就像一个魅力。非常感谢！

Answer 1

您的尝试无效，因为拥有的类型只能通过它们的 owner 实体进行配置，更具体地说，通过它们自己的构建器由 OwnsOne 方法返回或作为所有者实体生成器的 OwnsOne 方法的 Action<T> 参数的参数提供。

所以配置应该是这样的（注意嵌套OwnsOne）：

modelBuilder.Entity<Customer>(customer =>
{      
    customer.OwnsOne(e => e.Status, status =>
    {
        status.Property(e => e.Type).HasColumnName("Status");
        status.OwnsOne(e => e.ExpirationDate, expirationDate =>
        {
            expirationDate.Property(e => e.Date).HasColumnName("StatusExpirationDate");
        });
    });
});

Entity Framework 核心 2.1 - 自有类型和嵌套值对象

Entity Framework Core 2.1 - owned types and nested value objects

c#

domain-driven-design

value-objects

entity-framework-core-2.1

owned-types