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" });

我收到此错误：

未处理的类型＆＃39; System.InvalidOperationException＆＃39;   发生在EntityFramework.dll
中
附加信息：序列不包含匹配元素

这个错误意味着什么，我该如何纠正？可选地，有没有更好的方法来建模这个对象（例如：使用母语的子类：人和父：人）？ / p>

Answer 1

我提出了以下解决方案，它可以生成一个干净的数据库，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; }

结果数据库如下所示：

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;

Answer 2

我会做以下事情。虽然它可能不符合您的“实体框架”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(...
}

如何使用实体框架正确建模自引用多父关系

2 个答案: