EF Code首先，如何从一个表到另一个表实现两个外键？

Question

I've recently downloaded Entity Framework Code First CTP5 , and have a trouble with this scenario. I have two tables as follows:

Members table :
  ID  
  Name

Comments table :  
  ID  
  Comment  
  CommentedMemberID  
  CommentMemberID

And, the data should be like the following:

Members  
ID Name   
1  Mike  
2  John  
3  Tom  

Comments  
ID Comment CommentedMemberID CommentMemberID  
1  Good 1 2       
2  Good 1 3  
3  Bad  2 1

Then, I coded as shown below:

public class Member
{
    public int ID {get; set; }
    public string Name { get; set;}
    public virtual ICollection<Comment> Comments { get; set;}
}

public class Comment
{
    public int ID { get; set; }
    public string Comment { get; set; }
    public int CommentedMemberID { get; set; }
    public int CommentMemberID{ get; set; }

    public virtual Member CommentedMember { get; set; }
    public virtual Member CommentMember { get; set; }
}

public class TestContext : DbContext
{
    public DbSet<Member> Members { get; set; }
    public DbSet<Comment> Comments { get; set; }
}

But when I run these models on my cshtml , it gives me errors saying "Cannot create CommentMember instance" or something like that (Sorry, I already changed my models to proceed the EF Code First evaluation, so can't reproduce the same error).

I've also tried to use OnModelCreating on the TestContext , but can't find any good instructions and don't know what to do. I saw a blog post of the EF Code First CTP3, and it seems there was a RelatedTo attribute in that version, but now it has gone.

Could anyone know how to get it work properly? Or is this a totally wrong way to go with this scenario?

Thanks,
Yoo

Answer 1

This is a special case and you need to use fluent API to configure your associations. This will do the trick:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Comment>().HasRequired(c => c.CommentedMember)
                                  .WithMany(m => m.Comments)
                                  .HasForeignKey(c => c.CommentedMemberID)
                                  .WillCascadeOnDelete();

    modelBuilder.Entity<Comment>().HasRequired(c => c.CommentMember)
                                  .WithMany()
                                  .HasForeignKey(c => c.CommentMemberID)
                                  .WillCascadeOnDelete(false);
}