如何在Entity Framework中为第三个表添加额外的列？

问题描述

假设我有两个实体，用户和通知：

  public class User 
 {
 [Key] 
 public int UserId {get;组; } 
 
 //其他公共属性
 
 
 //导航属性
 
 public virtual ICollection< Notification>通知{get;组; 
} 
 
 
 
 public class Notification 
 {
 
 [Key] 
 public int NotificationId {get ;组; } 
 
 //其他公共属性
 
 //导航属性
 
 public virtual ICollection< User>用户{get;组; } 
 
} 
  

我只是添加多对多关系如下：

  modelBuilder.Entity< User>（）
 .HasMany（u => u.Notifications）
 .WithMany（t => t.Users）
 .Map（m => 
 {
 m。 ToTable（UserNotifications）; 
 m.MapLeftKey（UserId）; 
 m.MapRightKey（NotificationId）; 
}）; 
  

但是，如果我要为此表添加额外的列，那么该名称为'状态'？我以为我可以使用 AddColumn ，但是我如何访问这个列并获得它的价值？我该如何做到这一点？我想检查用户是否阅读通知。任何建议都会很好，谢谢。

解决方案

你不能在关系中添加额外的字段，如状态。你需要有一个虚拟表格。
我认为你的问题与以下答案相同

可能这将有所帮助。

Assume i have two entities, User and Notification:

public class User
{
[Key]
    public int UserId { get; set; }

// other public properties


// Navigation Properties

    public virtual ICollection<Notification> Notifications { get; set; }
}



public class Notification
{

    [Key]
    public int NotificationId { get; set; }

// other public properties

    // Navigation Properties

    public virtual ICollection<User> Users { get; set; }

}

I'm simply adding many-to-many Relationship like this:

modelBuilder.Entity<User>()
            .HasMany(u => u.Notifications)
            .WithMany(t => t.Users)
            .Map(m =>
            {
                m.ToTable("UserNotifications");
                m.MapLeftKey("UserId");
                m.MapRightKey("NotificationId");
            });

But what happens if i want to add extra column to this table which name is 'Status' ? I thought i can use AddColumn but then how can i access this column and get it's value ? How can i accomplish this? I want to check whether the user read notification or not. Any suggestions would be great,thanks.

解决方案

You can't add extra field like "Status" in the relationship. You need to have a dummy table for that.
And i think your question is same as the following answer
Many to Many mapping with extra fields in Fluent APIMay be this would help.

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