复合主键和外键 Code First

Question

我正在尝试创建 2 个实体，用户和用户评论，其中用户评论有一个复合主键，它是用户的 id，被评论的人和做评论的人，这个复合主键是也是用户 table 中主键的外键，但是 EF 正在创建一个额外的列，我看不到它的意义，当我将一个用户评论对象保存到数据库时，该列也没有'没有填充，它总是空的。

这导致当我尝试检索带有评论的用户时，评论集合始终为空，除非 User_SubjectId 列包含用户的 ID。

我的查询是这样的

 return _context.Users
                .Include(u => u.Reviews)
                .Where(u => u.SubjectId.Equals(subjectId));

评论集合总是空的

用户评论实体

using System;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace API.Data.Entities
{
    public class UserReview
    {
        [Key, Column(Order = 0), ForeignKey("Reviewer")]
        public string ReviewerId { get; set; } //The user that wrote the review

        [Key, Column(Order = 1), ForeignKey("ReviewedUser")]
        public string ReviewedUserId { get; set; } //The user who was reviewed

        [Required]
        [Range(1, 5)]
        public int Rating { get; set; }

        [Required]
        public DateTimeOffset DateCreated { get; set; }

        [Required]
        public virtual User Reviewer { get; set; }

        [Required]
        public virtual User ReviewedUser { get; set; }
    }
}

用户实体是这样的

public class User
    {
        [Key]
        [Required]
        public string SubjectId { get; set; }

        public User()
        {                
            Reviews = new List<UserReview>();
        }

        public virtual ICollection<UserReview> Reviews { get; set; }    
    }

但是，当我添加迁移时，会在我的 UserReviews table 中创建另一列，如图所示，该列是 User_SubjectId

我不知道这是 EF 中的错误还是我的映射有误，无论如何有什么想法吗？

谢谢

Answer 1

您必须使用反向属性注释。

public class UserReview
{
    [Key, Column(Order = 0), ForeignKey("Reviewer")]
    public string ReviewerId { get; set; } //The user that wrote the review

    [Key, Column(Order = 1), ForeignKey("ReviewedUser")]
    public string ReviewedUserId { get; set; } //The user who was reviewed

    [Required]
    [Range(1, 5)]
    public int Rating { get; set; }

    [Required]
    public DateTimeOffset DateCreated { get; set; }

    [Required]
    public virtual User Reviewer { get; set; }

    [Required)]
    public virtual User ReviewedUser { get; set; }
}

public class User
{
    [Key]
    [Required]
    public string SubjectId { get; set; }

    public User()
    {                
        Reviews = new List<UserReview>();
    }

    [InverseProperty("ReviewedUser")] // or Reviewer.
    public virtual ICollection<UserReview> Reviews { get; set; }    
}

在我看来，这是使用流畅映射时更容易配置的东西。

复合主键和外键 Code First

Composite primary keys and foreign keys Code First

c#

sql-server

entity-framework

ef-code-first

entity-framework-migrations