c# - 如何使用 Entity Framework 正确建模自引用多父关系

Question

我正在尝试在 EF6 中为以下自引用人员类建模。

public class Person
{
    public int ID { get; set; }
    public string Name { get; set; }

    public int? MotherId { get; set; }
    public Person Mother { get; set; }

    public int? FatherId { get; set; }
    public Person Father { get; set; }

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

我的 DbContext 看起来像这样:

public virtual DbSet<Person> People { get; set; }

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<Person>()
        .HasOptional(m => m.Mother)
        .WithMany(c => c.Children)
        .HasForeignKey(m => m.MotherId);

     modelBuilder.Entity<Person>()
        .HasOptional(f => f.Father)
        .WithMany(c => c.Children)
        .HasForeignKey(f => f.FatherId);
}

尝试使用以下代码将人员添加到数据库时:

db.People.Add(new Person { Name = "Jane Doe" });

我收到这个错误:

An unhandled exception of type 'System.InvalidOperationException' occurred in EntityFramework.dll

Additional information: Sequence contains no matching element

这个错误是什么意思，我该如何纠正它？是否有更好的方法来模拟这个对象(例如:使用 Mother:Person 和 Father:Person 的子类)？

Answer 1

我提出了以下解决方案，可以生成干净的数据库并在添加关系时提供更大的灵 active :

public interface IParent
{
    ICollection<Person> Children { get; set; }
}

public class Person
{
    public int ID { get; set; }
    public string Name { get; set; }

    public int? MotherId { get; set; }
    public Female Mother { get; set; }

    public int? FatherId { get; set; }
    public Male Father { get; set; }
}

public class Male : Person, IParent
{
    public virtual ICollection<Person> Children { get; set; }
}

public class Female : Person, IParent
{
    public virtual ICollection<Person> Children { get; set; }
}

DbContext 仅包含:

public virtual DbSet<Person> People { get; set; }
public virtual DbSet<Female> Females { get; set; }
public virtual DbSet<Male> Males { get; set; }

生成的数据库如下所示:

ID  Name    MotherId    FatherId    Discriminator
1   Jane    NULL        NULL        Female
2   John    NULL        NULL        Male
3   Jimmy   1           2           Male
4   Jenn    1           2           Female

此解决方案还提供了以多种方式添加关系的灵 active :

mom.Children.Add(son); // or
son.Mother = mom;