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; }

}

我的基类只有三个属性：ID，CreateDate和IsDeleted，没有一个与User类相关：

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会创建一个额外的列User_ID，始终为null ，如下所示：

它显然没有映射到任何东西。我的其他实体（无论是否来自相同的基类）都没有此幻像列。为什么要创建此列？我使用SQL Azure在EF 6.1.3代码优先。

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

更新2：甚至在列上定义了索引和外键。我已经尝试删除它（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类的导航属性配置不正确。由于Notification类没有名为User的属性，而是Receiver，因为我忘了添加正确的名称（Receiver）作为反向属性我的User类有一个Notifications集合，这个额外字段用于将从{/ 1>} 导航到 User秒。我已将注释Notification添加到[InverseProperty("Receiver")]类的我的集合中，现在它可以正常运行。

Answer 2

您可以使用数据公式：

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：

Many to many relation

Navigation property

为什么Entity Framework会创建一个不映射到任何字段的额外列，并且始终为null？

2 个答案: