entity-framework - 集合的 EF Code First 映射

Question

我首先使用 EF 4.1 RC 代码。我在连接表 Friends 中有一个使用复合 PK 的多对多关系。我们明确需要一个单独的 Friends 类(不要问)来代表我们的联结表。我们的目标是能够控制用户实体的删除过程。请在阅读其余部分之前阅读此内容:http://mocella.blogspot.com/2010/01/entity-framework-v4-object-graph.html 。因此，我们设法创建了复合 PK，但这破坏了我们的集合映射。问题是如何映射FriendsCol？

public class User
{
    public int UserId { get; set; }
    public string Name { get; set; }
    public virtual ICollecion<Friends> FriendsCol { get; set; }

}

public class Friends
{
    public int User1Id { get; set; }
    public int User2Id { get; set; }

    public User User1 { get; set; }
    public User User2 { get; set; }

}

有一个复合键映射

public class FriendsMap : EntityTypeConfiguration<Friends>
{
  HasKey(m => new { m.userId1 , m.userId2 });

  //this.HasRequired(x => x.User1)
  //.WithMany()
  //.HasForeignKey(x => x.User1Id)
  //.WillCascadeOnDelete(false);

  //this.HasRequired(x => x.User2)
  //    .WithMany()
  //    .HasForeignKey(x => x.User2Id)
  //    .WillCascadeOnDelete(false);
}

public class UserMap : EntityTypeConfiguration<UserNew>
{
  public UserMap()            
  {
    ToTable("users");
    Property(user => user.Name).HasColumnName("name");
    // HasMany<Friends>(user => user.FriendsCol).WithMany();

  }
}

Answer 1

这个怎么样:

public class FriendsMap : EntityTypeConfiguration<Friends>
{
  HasKey(m => new { m.userId1 , m.userId2 });

  this.HasRequired(x => x.User1)
      .WithMany()
      .HasForeignKey(x => x.User1Id)
      .WillCascadeOnDelete(false);

  this.HasRequired(x => x.User2)
      .WithMany(u => u.FriendsCol)
      .HasForeignKey(x => x.User2Id)
      .WillCascadeOnDelete(false);
}

public class UserMap : EntityTypeConfiguration<UserNew>
{
  public UserMap()            
  {
    ToTable("users");
    Property(user => user.Name).HasColumnName("name");
  }
}

编辑:

我只是做了一个非常简单的例子，它的工作没有任何问题:

class Program
{
    static void Main(string[] args)
    {
         using (var context = new Context())
         {
             context.Database.Delete();
             context.Database.CreateIfNotExists();

             var u1 = new User() { Name = "A" };
             var u2 = new User() { Name = "B" };
             var u3 = new User() { Name = "C" };

             var f1 = new Friends() { User1 = u1, User2 = u2};
             var f2 = new Friends() { User1 = u1, User2 = u3 };

             context.Friends.Add(f1);
             context.Friends.Add(f2);
             context.SaveChanges();
         }
    }
}

public class User
{
    public int UserId { get; set; }
    public string Name { get; set; }
    public virtual ICollection<Friends> FriendsCol { get; set; }
}

public class Friends
{
    public int User1Id { get; set; }
    public int User2Id { get; set; }

    public User User1 { get; set; }
    public User User2 { get; set; }

}

public class Context : DbContext
{
    public DbSet<User> Users { get; set; }
    public DbSet<Friends> Friends { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        modelBuilder.Entity<Friends>()
            .HasKey(m => new { m.User1Id, m.User2Id });

        modelBuilder.Entity<Friends>()
            .HasRequired(x => x.User1)
            .WithMany()
            .HasForeignKey(x => x.User1Id)
            .WillCascadeOnDelete(false);

        modelBuilder.Entity<Friends>()
            .HasRequired(x => x.User2)
            .WithMany(u => u.FriendsCol)
            .HasForeignKey(x => x.User2Id)
            .WillCascadeOnDelete(false);

    }
}