实体框架类问题中有两个相同的类类型 [英] Two same class types in entity framework class issue

问题描述

我正在实施功能，允许用户互相追踪。
我有数据库表：

I am implementing feature that allows users to follow each other. I have database tables:

User{UserId, FirstName, LastName etc.}
Followings{FollowerUserId, FollowingUserId, CreatedOnDate etc.}

所以我添加了EF类：

public class Follow
    {
        [Key, Column(Order = 1)]
        public Guid FollowerUserId { get; set; }
        [Key, Column(Order = 2)]
        public Guid FollowUserId { get; set; }        
        public DateTime CreatedOnDate { get; set; }

        public virtual User Follower { get; set; }
        public virtual User Following { get; set; }
    }

最后两个虚拟属性有问题。
当我打电话：

The last two virtual properties couse issue. When I call:

var model = con.Follows.Where(x => x.FollowerUserId == uid);

我收到以下异常：

Invalid column name 'Following_UserId'.

问题可能是由于一个类中的两个User对象引起的。任何想法如何解决这个问题？

更新

The issue is probably caused because of two User objects in one class. Any idea how to workaround this?
UPDATE

public class User
    {

        public Guid UserId { get; set; }
        ...
        public virtual ICollection<Follow> Following { get; set; }
        public virtual ICollection<Follow> Followers { get; set; }
    }

推荐答案

外键属性（ FollowerUserId 和 FollowUserId ）和导航属性（跟随者和以下）不遵守命名约定，因此EF无法将第一个属性识别为外键。您可以通过使用 [ForeignKey] 属性明确指定FK属性来解决问题：

I think the reason is that the foreign key properties (FollowerUserId and FollowUserId) and navigation properties (Follower and Following) do not respect the naming conventions so that EF is unable to recognize the first properties as foreign keys. You can fix the problem by specifying the FK properties explicitly using the [ForeignKey] attribute:

public class Follow
{
    [Key, Column(Order = 1), ForeignKey("Follower")]
    public Guid FollowerUserId { get; set; }
    [Key, Column(Order = 2), ForeignKey("Following")]
    public Guid FollowUserId { get; set; }        

    public DateTime CreatedOnDate { get; set; }

    public virtual User Follower { get; set; }
    public virtual User Following { get; set; }
}

修改

至少第二个属性不遵守命名约定，第一个属性看起来不错。所以，或者您可以通过将第二个FK属性 FollowUserId 重命名为：

A least the second property doesn't respect the naming convention, the first one looks OK. So, alternatively you can fix the problem by renaming the second FK property FollowUserId into:

public Guid FollowingUserId { get; set; }        

...因为导航属性被称为跟随。

...because the navigation property is called Following.

编辑2

关于您的更新：您需要添加 [InverseProperty] 属性来告诉EF哪些导航属性属于一起：

About your UPDATE: You need to add the [InverseProperty] attribute to tell EF which navigation properties belong together:

public class Follow
{
    [Key, Column(Order = 1), ForeignKey("Follower")]
    public Guid FollowerUserId { get; set; }
    [Key, Column(Order = 2), ForeignKey("Following")]
    public Guid FollowUserId { get; set; }        

    public DateTime CreatedOnDate { get; set; }

    [InverseProperty("Followers")]  // refers to Followers in class User
    public virtual User Follower { get; set; }
    [InverseProperty("Following")]  // refers to Following in class User
    public virtual User Following { get; set; }
}

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