How can i add extra column to third table in Entity Framework?

问题

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.

回答1:

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

来源：https://stackoverflow.com/questions/20673785/how-can-i-add-extra-column-to-third-table-in-entity-framework