如果有两个自身的外键，则EF Core自引用不起作用（代码优先） [英] EF Core self referencing not working if there are 2 foreign keys to self (Code first)

问题描述

如果我（首先在代码中）为自身定义了一个导航属性，则它可以工作（创建外键），但是如果我定义2，则它不起作用。

如何创建2个自我的外键？基于文档

If I defined (in code first) one navigation property to self it works (foreign key is created), but if I define 2 it doesn't work.
How can I create 2 foreign keys to self? Based on documentation by conventions they should be created.

例如，此方法有效（创建了外键）：

For example this works (foreign key is created):

public class DbPart 
{
    [Key]
    [Required]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    [ForeignKey("Source")]
    public int? SourceId { get; set; }
    public DbPart Source { get; set; }

    [InverseProperty("Source")]
    public List<DbPart> SourceParts { get; set; }
}

也是这样：

public class DbPart 
{
    [Key]
    [Required]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    [ForeignKey("SourceFake")]
    public int? SourceFakeId { get; set; }
    public DbPart SourceFake { get; set; }

    [InverseProperty("SourceFake")]
    public List<DbPart> SourceFakeParts { get; set; }
}

但不是这样：

public class DbPart 
{
    [Key]
    [Required]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    [ForeignKey("Source")]
    public int? SourceId { get; set; }
    public DbPart Source { get; set; }


    [ForeignKey("SourceFake")]
    public int? SourceFakeId { get; set; }
    public DbPart SourceFake { get; set; }

    [InverseProperty("SourceFake")]
    public List<DbPart> SourceFakeParts { get; set; }

    [InverseProperty("Source")]
    public List<DbPart> SourceParts { get; set; }
}

我还有另一个例子，我在数据库中写树结构，但是而不是只写ParentId，我也写RootId。同样，在将2个属性引用到self（ParentId，RootId）时，不会创建外键。

I also have another example, where I write tree structure in database, but instead writing just ParentId, I also write RootId. Again, foreign key is not created when referencing 2 properties to self (ParentId, RootId).

已编辑：

由于此错误，它无法正常工作。简便的解决方案是从ID属性中删除[Key]或在Steve Greene答案中使用流利的解决方案。还请此处。

Edited:
It is not working because of this bug. Easy solution is to remove [Key] from Id property or use fluent solution in Steve Greene answer. Check also here.

推荐答案

我更喜欢这些内容的流利代码：

I prefer the fluent code for this stuff:

modelBuilder.Entity<DbPart>()
    .HasOne(p => p.Source)
    .WithMany(p => p.SourceParts)
    .HasForeignKey(p => p.SourceId);

modelBuilder.Entity<DbPart>()
    .HasOne(p => p.SourceFake)
    .WithMany(p => p.SourceFakeParts)
    .HasForeignKey(p => p.SourceFakeId);

但是如果您想要注释，请尝试以下操作：

But if you want annotations try this:

public class DbPart 
{
    public int Id { get; set; }   // Key & Indentity by convention

    public int? SourceId { get; set; }  // FK by convention
    [InverseProperty("SourceParts")]
    public DbPart Source { get; set; }

    public int? SourceFakeId { get; set; } // FK by convention
    [InverseProperty("SourceFakeParts")]
    public DbPart SourceFake { get; set; }

    [InverseProperty("SourceFake")]
    public List<DbPart> SourceFakeParts { get; set; }

    [InverseProperty("Source")]
    public List<DbPart> SourceParts { get; set; }
}

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