我从两个外键引用到两个不同的表中创建复合键时出错

Posted 2023-02-26

【中文标题】我从两个外键引用到两个不同的表中创建复合键时出错

【英文标题】：ihave an error with making composite key from two foreign key references to two different tables

【发布时间】：2016-04-24 12:09:01

【问题描述】：

我有 3 个模型用户、ArticleComments 和 UserSubsription .. 我试图将 3 个道具作为复合键，其中两个是对两个不同表的外键引用，但我在尝试启用迁移时出错

用户.CS

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Web;
using WebAppInternetApp.Models;

namespace WebAppInternetApp.Models

    public class User
    

        public User()
        
            this.WriterIDs = new HashSet<JobArticle>();
            this.AdminIDs = new HashSet<JobArticle>();
            this.UserIDs = new HashSet<ArticleComments>();
            this.UserIDss = new HashSet<UserQuestion>();
            this.UseerIDsss = new HashSet<UserSubscription>();
        

        [Key]
        public int UID  get; set; 

        [Required]
        [StringLength(20, MinimumLength = 2)]
        public string FName  set; get; 

        [Required]
        [StringLength(20, MinimumLength = 2)]
        public string LName  set; get; 

        [Required]
        [DataType(DataType.EmailAddress)]
        public string Email  set; get; 

        [Required]
        [StringLength(25, MinimumLength = 8)]
        public string Password  set; get; 

        [Required]
        public bool Status  set; get; 

        [Required]
        [Phone]
        public string PhoneNo  set; get; 

        [Column(TypeName = "image")]
        public byte[] UserImg  set; get; 

        public virtual ICollection<JobArticle> WriterIDs  set; get; 
        public virtual ICollection<JobArticle> AdminIDs  set; get; 
        public virtual ICollection<ArticleComments> UserIDs  set; get; 
        public virtual ICollection<UserQuestion> UserIDss  set; get; 
        public virtual ICollection<UserSubscription> UseerIDsss  set; get; 

        public virtual UserType usertypeIDs  set; get; 



    

文章评论.CS

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace WebAppInternetApp.Models

    public class ArticleComments
    
        [Required]
        public string Comment  set; get; 
        [Key]
        [Column(Order = 0)]
        public DateTime CommentTime  set; get; 
        [Key]
        [Column(Order = 1)]
        [ForeignKey("User")]
        public virtual User UserID  set; get; 
        [Key]
        [Column(Order = 2)]
        [ForeignKey("JobArticle")]
        public virtual JobArticle ArticleID  set; get; 
    

UserSubsription.CS

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Web;
using WebAppInternetApp.Models;

namespace WebAppInternetApp.Models

    public class UserSubscription
    
        [Key]
        [Column(Order = 0)]
        [ForeignKey("User")]
        public virtual User UserIDs  set; get; 

        [Key]
        [Column(Order = 1)]
        [ForeignKey("JobCategory")]
        public virtual JobCategory SubscriptID  set; get; 
    

【问题讨论】：

你遇到了什么错误？

“WebAppInternetApp.Models.ArticleComments”类型的属性“ArticleID”上的 ForeignKeyAttribute 无效。在依赖类型“WebAppInternetApp.Models.ArticleComments”上找不到外键名称“JobArticle”。 Name 值应该是一个逗号分隔的外键属性名称列表。

【参考方案1】：

基于微软description of the ForeignKeyAttribute:

如果将 ForeigKey 属性添加到外键属性，则 应指定关联导航属性的名称。如果你 将 ForeigKey 属性添加到导航属性，您应该 指定关联外键的名称。如果一个导航 属性有多个外键，使用逗号分隔列表 外键名

在您的代码中，您没有定义外键属性。您只需定义导航属性。

查看这篇文章了解如何使用 ForeignKey 属性：

Understanding ForeignKey attribute in entity framework code first

例如，您的 UserSubscription 应如下所示：

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Web;
using WebAppInternetApp.Models;

namespace WebAppInternetApp.Models

    public class UserSubscription
    
        [Key]
        [Column(Order = 0)]
        [ForeignKey("User")]
        public int UserIDs  set; get; 

        [Key]
        [Column(Order = 1)]
        [ForeignKey("JobCategory")]
        public int SubscriptID  set; get; 

        // those are the navigation properties
        public virtual User User  set; get; 
        public virtual JobCategory JobCategory  set; get; 
    

ArticleComments 可能是这样的：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace WebAppInternetApp.Models

    public class ArticleComments
    
        [Required]
        public string Comment  set; get; 

        [Key]
        [Column(Order = 0)]
        public DateTime CommentTime  set; get; 

        [Key]
        [Column(Order = 1)]
        [ForeignKey("User")]
        public int UserID  set; get; 

        [Key]
        [Column(Order = 2)]
        [ForeignKey("JobArticle")]
        public int ArticleID  set; get; 

        public virtual User User  set; get; 
        public virtual JobArticle JobArticle  set; get; 

    

【讨论】：

如果我删除外键，我收到此消息“WebAppInternetApp.Models.UserSubscription: : EntityType 'UserSubscription' 没有定义键。定义此 EntityType 的键。UserSubscriptions: EntityType: EntitySet 'UserSubscriptions' 是基于没有定义键的“UserSubscription”类型。"

但它会为用户 ID 和文章 ID 创建两个属性！

我在尝试此 WebAppInternetApp.Models.UserSubscription: 时收到此消息：：EntityType 'UserSubscription' 没有定义密钥。定义此 EntityType 的键。 UserSubscriptions：EntityType：EntitySet 'UserSubscriptions' 基于没有定义键的类型 'UserSubscription'。