Entity Framework 多次引用相同 table

Question

我在使用 EF 代码优先创建数据库时遇到问题。我有一个实体 Player 和一个实体 friedship。

每个友谊都引用了两个玩家。其中一位玩家是友谊的发送者，另一位是友谊的接收者。

这是我的实体：

Player.cs

public class Player
{
    public int PlayerId { get; set; }

    [Required]
    public string Name { get; set; }

    [Required]
    public string Email { get; set; }

    [InverseProperty("Receiver")]
    public virtual List<Friendship> FriendshipsIncoming { get; set; }

    [InverseProperty("Sender")]
    public virtual List<Friendship> FriendshipsOutgoing { get; set; }
}

Friendship.cs

public class Friendship
{
    public int FriendshipId { get; set; }

    public int SenderId { get; set; }
    public int ReceiverId { get; set; }

    [ForeignKey("Sender")]
    public Player Sender { get; set; }

    [ForeignKey("Receiver")]
    public Player Receiver { get; set; }

    [Required]
    public bool Confirmed { get; set; }
}

我尝试按照本教程中所示的方式实现关系： http://www.entityframeworktutorial.net/code-first/inverseproperty-dataannotations-attribute-in-code-first.aspx

尝试使用 "update-database" 命令更新数据库时，出现以下错误消息：

The ForeignKeyAttribute on property 'Receiver' on type 'Darta.WebApi.Models.Friendship' is not valid. The foreign key name 'Receiver' was not found on the dependent type 'Darta.WebApi.Models.Friendship'. The Name value should be a comma separated list of foreign key property names.

我还尝试使用 fluent-api 解决问题，如下所示： http://csharpwavenet.blogspot.sg/2013/06/multiple-foreign-keys-with-same-table.html

protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Friendship>()
            .HasRequired(b => b.Sender)
            .WithMany(a => a.FriendshipsOutgoing)
            .HasForeignKey(b=>b.SenderId);

        modelBuilder.Entity<Friendship>()
            .HasRequired(b => b.Receiver)
            .WithMany(a => a.FriendshipsIncoming)
            .HasForeignKey(b => b.ReceiverId);
    }

在这种情况下，我收到以下错误：

Introducing FOREIGN KEY constraint 'FK_dbo.Friendships_dbo.Players_SenderId' on table 'Friendships' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints. Could not create constraint or index. See previous errors.

Answer 1

您应该只需要 DataAnnotations 或 FluentAPI。你不需要两者。如果要使用 [ForeignKey] 和 [InverseProperty] 属性，请去掉 FluentAPI 代码。

另请注意，在[ForeignKey]和[InverseProperty]属性中，您需要指定列的名称，而不是导航属性。

public class Player
{
    public int PlayerId { get; set; }

    [Required]
    public string Name { get; set; }

    [Required]
    public string Email { get; set; }

    [InverseProperty("ReceiverId")]
    public virtual ICollection<Friendship> FriendshipsIncoming { get; set; }

    [InverseProperty("SenderId")]
    public virtual ICollection<Friendship> FriendshipsOutgoing { get; set; }
}

public class Friendship
{
    public int FriendshipId { get; set; }

    public int SenderId { get; set; }
    public int ReceiverId { get; set; }

    [ForeignKey("SenderId")]
    public Player Sender { get; set; }

    [ForeignKey("ReceiverId")]
    public Player Receiver { get; set; }

    [Required]
    public bool Confirmed { get; set; }
}

Answer 2

我会更正答案。 InverseProperty 必须是有效的实体类型。所以在这种情况下 Friendship.Receiver, Friendship.Sender

public class 玩家 { public int PlayerId { 得到;放; }

   [Required]
   public string Name { get; set; }

   [Required]
   public string Email { get; set; }

   [InverseProperty("Receiver")]
   public virtual ICollection<Friendship> FriendshipsIncoming { get; set; }

   [InverseProperty("Sender")]
   public virtual ICollection<Friendship> FriendshipsOutgoing { get; set; }

}

publicclass友情 { public int FriendshipId { 得到;放; }

   public int SenderId { get; set; }
   public int ReceiverId { get; set; }

   [ForeignKey("SenderId")]
   public Player Sender { get; set; }

   [ForeignKey("ReceiverId")]
   public Player Receiver { get; set; }

   [Required]
   public bool Confirmed { get; set; }

}

Entity Framework 多次引用相同 table

Entity Framework multiple references to same table

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