Entity framework 如何在实体类中有两个自引用

我有一个

Foo

，它本身可以有两个可选的引用：

ParentId

和

RootId

public class Foo
{
    [Key]
    public int FooId { get; set; }

    public int? ParentId { get; set; }

    [ForeignKey(nameof(ParentId))]
    public virtual Foo Parent { get; set; }

    public int? RootId { get; set; }

    [ForeignKey(nameof(RootId))]
    public virtual Foo RootFoo { get; set; }

    // ...
}

有一个很好，但当我引入第二个自参考时，我得到了错误：

无法确定类型“Model.Foo”和“Model.Foo”之间关联的主体端。必须使用关系fluent API或数据注释显式配置此关联的主体端

修正

EF想知道从Foo的另一面看，这些关系是什么样子的，即：

Foo has one Parent / but a Parent, how many Foos has?
Foo has one RootFoo / but a RootFoo, how many Foos has?

使用Fluet API：

var foo = modelBuilder.Entity<Foo>().ToTable("Foo", schemaName);
foo.HasOptional(a => a.Parent).WithMany();
foo.HasOptional(a => a.RootFoo).WithMany();

public class Foo
{
    [Key]
    public int FooId { get; set; }

    public int? ParentId { get; set; }

    [ForeignKey(nameof(ParentId))]
    public virtual Foo Parent { get; set; }

    [InverseProperty("Parent")]
    public virtual ICollection<Foo> SingleLevelChildren { get; set; }

    public int? RootFooId { get; set; }

    [ForeignKey(nameof(RootFooId))]
    public virtual Foo RootFoo { get; set; }

    [InverseProperty("RootFoo")]
    public virtual ICollection<Foo> AllChildren { get; set; }

    // ...
}