EF Core中带有复合键的外键

问题描述

限时删除！！

我有以下类：

    public class ProductAttribute
    {
        public Guid ProductId { get; set; }

        public Guid AttributeId { get; set; }

        public List<ProductAttributeValue> Values { get; set; }

        public object[] GetKeys()
        {
            return new object[] {ProductId, AttributeId};
        }
    }

    public class Product
    {
        public Guid Id { get; set; }

        public string Name { get; set; }
    }

    public class Attribute
    {
        public Guid Id { get; set; }

        public string Name { get; set; }
    }

    public class ProductAttributeValue
    {
        public Guid Id { get; set; }

        public string Name { get; set; }
    }

在原始情况下，Product和Attribute是AggregateRoot，所以我想跳过属性参考。值是一个简单的实体，但是您需要在我的ProductAttribute类中将其作为列表引用，因为您看到该类具有复合键。但是我想要在ProductAttribute
和ProductAttributeValue之间与级联删除建立必要的关系。

In origin case Product and Attribute are AggregateRoot so I want skip navigate that by property references. Value is a simple entity but I need that as list reference in my ProductAttribute class as you see that class have composite key. But I want a required relationship with cascade delete between ProductAttribute and ProductAttributeValue.

该项目是外部模块，所以我流畅的API配置是扩展，在目标应用程序DbContext OnModelCreating中调用。我应该配置每个属性，否则其他引用将不起作用。

This project is external module, so my fluent API configurations are extension which called in target app DbContext OnModelCreating. I should config every properties and references else didn't work.

        builder.Entity<ProductAttribute>(b =>
        {
            b.ToTable("ProductAttributes");

            b.HasKey(x => new {x.ProductId, x.AttributeId});

            //I should config ProductAttributeValue one-to-many manually here
        }

        builder.Entity<Product>(b =>
        {
            b.ToTable("Products");

            b.HasKey(x => x.Id);
        }

        builder.Entity<Attribute>(b =>
        {
            b.ToTable("Attributes");

            b.HasKey(x => x.Id);
        }

        builder.Entity<ProductAttributeValue>(b =>
        {
            b.ToTable("ProductAttributeValues");

            b.HasKey(x => x.Id);

            //I should config ProductAttribute many-to-one manually here
        }

如何为ProductAttribute实体配置Fluent API以通过这种情况？

How can you configure your Fluent API for ProductAttribute entity to passing this scenario?

推荐答案

为了根据需要配置所需的关系并进行级联删除，可以在<$ c $中使用以下内容c> ProductAttribute 实体配置块：

In order to configure the desired relationship as required and cascade delete, you can use the following inside the ProductAttribute entity configuration block:

b.HasMany(e => e.Values)
    .WithOne()
    .IsRequired();

IsRequired 就足够了，因为按照惯例，级联删除为必需关系打开，为可选关系关闭。当然，如果需要，您可以添加 .OnDelete（DeleteBehavior.Cascade）-这是多余的，但不会造成伤害。

IsRequired is enough because by convention cascade delete is on for required and off for optional relationships. Of course you can add .OnDelete(DeleteBehavior.Cascade) if you want - it will be redundant, but won't hurt.

请注意，应在单个位置配置关系。因此，请在 ProductAttribute 或 ProductAttributeValue 中执行此操作，但不要同时在两者中进行（容易出错，可能会导致意外的冲突或覆盖配置

Please note that the relationships should be configured in a single place. So do it either in ProductAttribute or ProductAttributeValue, but never in both (error prone, may cause unexpected conflicting or overriding configuration issues).

为完整起见，这是您可以在 ProductAttributeValue 配置中配置相同内容的方法（要求显式提供 HasOne 泛型类型参数（由于缺少导航属性）：

For completeness, here is how you can configure the same inside ProductAttributeValue configuration (requires explicitly providing the HasOne generic type argument due to the lack of navigation property):

b.HasOne<ProductAttribute>()
    .WithMany(e => e.Values)
    .IsRequired();

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