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 中为以下自引用人建模 class。

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，我该如何更正它？ 或者，是否有更好的方法来建模这个对象（例如：使用 subclass Mother:Person 和 Father:Person)?

Answer 1

我会做以下事情。尽管它可能不符合您的 'In Entity Framework' 要求

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

    public int? MotherId { get; set; }
    public int? FatherId { get; set; }
}

public Class RelationFinder
{
    Public Person GetMother(IEnumerable<Person> people, Person child)
    {
        return people.FirstOrDefault(p=>p.Id = child.MotherId);
    }

    Public Person GetFather(...

    Public IEnumerable GetChildern(...
}

Answer 2

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活性：

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活性：

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

如何使用 entity framework 正确建模自引用多父关系

How to correctly model self-referencing multi-parent relationship using entity framework

c#

entity-framework

entity-framework-6