为什么 Entity Framework 创建一个不映射到任何字段且始终为空的额外列？

Question

我的 POCO 设置如下：

public class Notification : BaseClass
{

    public User Receiver { get; set; }

    [Required, Index]
    public long ReceiverID { get; set; }

    public virtual User ContextualUser { get; set; }

    public long? ContextualUserID { get; set; }

    public virtual User Actor { get; set; }

    public long? ActorID { get; set; }

    public string Content { get; set; }

    public string Uri { get; set; }

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

}

我的基地class只有三个属性：ID、CreateDate和IsDeleted、none 与 User class:

有关

public abstract class BaseClass
{
    [Key]
    public long ID { get; set; }

    [Required]
    public DateTime CreateDate { get; set; }

    public bool IsDeleted { get; set; }

    public BaseClass()
    {
        CreateDate = DateTime.UtcNow;
    }
}

但是，Entity Framework 创建了一个额外的列 User_ID，它 始终为 null，如下所示：

它显然没有映射到任何东西。 None 我的其他实体（无论是否源自相同的基础 class）都有这个 phantom 列。为什么要创建这个专栏？我在 EF 6.1.3 代码优先上使用 SQL Azure。

更新： 我也在 PM 控制台中运行 update-database 但没有任何改变，我仍然有这个专栏。

更新 2: 甚至在列上定义了一个索引和一个外键。我试过删除它（它还不是一个实时应用程序）但它被索引引用：

alter table notifications drop column User_ID

Msg 5074, Level 16, State 1, Line 1
The index 'IX_User_ID' is dependent on column 'User_ID'.
Msg 5074, Level 16, State 1, Line 1
The object 'FK_dbo.Notifications_dbo.Users_User_ID' is dependent on column 'User_ID'.
Msg 4922, Level 16, State 9, Line 1
ALTER TABLE DROP COLUMN User_ID failed because one or more objects access this column.

Answer 1

我的 User class 上的导航属性配置不正确。因为 Notification class 没有名为 User 的属性而是 Receiver，并且因为我忘记添加正确的名称（接收者）作为我的 User class 上的逆向属性有一个 Notifications collection，这个额外的字段是为了从 从 [=24= 导航而生成的] User 至 Notification秒。我已经在 User class 上向我的 collection 添加了注释 [InverseProperty("Receiver")]，它现在可以正常工作了。

Answer 2

您可以为此使用数据注释：

public abstract class BaseClass
{
    [Key]
    public long ID { get; set; }

    [Required]
    public DateTime CreateDate { get; set; }

    public bool IsDeleted { get; set; }

    public BaseClass()
    {
        CreateDate = DateTime.UtcNow;
    }
}

public class Notification : BaseClass
{
    [ForeignKey("ReceiverID")]
    [InverseProperty("Receivers")]
    public User Receiver { get; set; }

    [Required, Index]
    public long ReceiverID { get; set; }


    [ForeignKey("ContextualUserID")]
    [InverseProperty("ContextualUsers")]
    public virtual User ContextualUser { get; set; }

    public long? ContextualUserID { get; set; }


    [ForeignKey("ActorID")]
    [InverseProperty("Actors")]
    public virtual User Actor { get; set; }

    public long? ActorID { get; set; }

    public string Content { get; set; }

    public string Uri { get; set; }

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

}

public class User
{
    [InverseProperty("Receiver")]
    public ICollection<Notification> Receivers { get; set; }

    [InverseProperty("ContextualUser")]
    public ICollection<Notification> ContextualUsers { get; set; }

    [InverseProperty("Actor")]
    public ICollection<Notification> Actors { get; set; }
}

了解更多信息：

为什么 Entity Framework 创建一个不映射到任何字段且始终为空的额外列？

Why is Entity Framework creating an extra column that doesn't map to any field and is always null?

sql-server

entity-framework

ef-code-first