实体框架代码优先:如何映射多个自引用多对多关系 [英] Entity Framework Code First: how to map multiple self-referencing many-to-many relationships

问题描述

我创建了一个实体类型，该实体类型具有多个引用相同类型项目的集合属性.换句话说，它反映了一个数据库表，其中的行被任意分组，这样一行就可以出现在多个组中.

I have created an entity type that has multiple collection properties that reference items of the same type. In other words, it reflects a single database table in which the rows are arbitrarily grouped, such that a row may appear in multiple groups.

在下面的简化示例中，Person类具有Brothers和Sisters集合属性，它们也引用Person实体:

In the following simplified example, the Person class has Brothers and Sisters collection properties that also reference Person entities:

public class Person
{
    public Person()
    {
        Brothers = new Collection<Person>();
        Sisters = new Collection<Person>();
    }

    [Key]
    public string Name { get; set; }

    public int Age { get; set; }

    public virtual ICollection<Person> Brothers { get; set; } 

    public virtual ICollection<Person> Sisters { get; set; } 
}

实体框架似乎认为这是一个有效的模型，但是将其解释为创建单个PersonPersons连接表，该表无法反映兄弟姐妹关系的分离.

Entity Framework seems to think that this is a valid model, but interprets it to create a single PersonPersons join table, which fails to reflect the separation of brother and sister relationships.

我认为解决方案是使用fluent API为两个关系显式映射单独的联接表，但是尽管进行了广泛的实验，我仍然无法使它起作用.

I assume the solution is to use the fluent API to explicitly map separate join tables for the two relationships but, despite extensive experimentation, I have been unable to get this to work.

有什么建议吗?

谢谢， 蒂姆

推荐答案

通过在DbContext.OnModelCreating方法中添加它:

By adding this in the DbContext.OnModelCreating method:

更新根据上面的nameEqualsPNamePrubeGoldberg的评论添加了表命名映射:

UPDATE Added table-naming map according to nameEqualsPNamePrubeGoldberg's comment above:

modelBuilder.Entity<Person>().HasMany(x => x.Brothers).WithMany()
    .Map(x => x.ToTable("Person_Brothers"));
modelBuilder.Entity<Person>().HasMany(x => x.Sisters).WithMany()
    .Map(x => x.ToTable("Person_Sisters"));

我通过了这个单元测试

[TestMethod]
public void TestPersons()
{
    var brother = new Person() { Name = "Brother 1", Age = 10 };
    var sister = new Person() { Name = "Sister 1", Age = 12 };
    var sibling = new Person() { Name = "Sibling 1", Age = 18 };
    sibling.Brothers.Add(brother);
    sibling.Sisters.Add(sister);

    using (var db = new MyDatabase())
    {
        db.Persons.Add(brother);
        db.Persons.Add(sister);
        db.Persons.Add(sibling);

        db.SaveChanges();
    }

    using (var db = new MyDatabase())
    {
        var person = db.Persons
            .Include(x => x.Sisters)
            .Include(x => x.Brothers)
            .FirstOrDefault(x => x.Name.Equals(sibling.Name));

        Assert.IsNotNull(person, "No person");
        Assert.IsTrue(person.Brothers.Count == 1, "No brothers!");
        Assert.IsTrue(person.Sisters.Count == 1, "No sisters");
    }
}

这还会创建您正在谈论的链接表.

That also creates the link tables you're talking about.

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