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
在Fluent API中与多个字段进行多对多映射
可能这将有所帮助。

用户
通知_
您将状态字段字段的UserNotification（虚拟表） p>

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.

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 API May be this would help.

User
Notification
UserNotification (dummy table) where you put your Status field