我需要在两个代码优先的实体之间创建一个复杂的关系，但是我很难缠着它

Question

I have two entities and these two entities have two different relationships between one another. The first relationship is a one to many relationship and the second relationship is a many to many relationship. See the entities below.

public class User
{
    public int Id { get; set; }
    public string Password { get; set; }
    public string Name { get; set; }

    // Collection that represent this user's attached social providers.
    public virtual ICollection<SocialProvider> SocialProviders { get; set; }
    // Collection representing this user's friends from her attached social providers.
    public virtual ICollection<SocialProvider> SocialContacts { get; set; }
}

public enum Provider
{
    Google,
    Facebook,
    Twitter
}

public class SocialProvider
{
    public int Id { get; set; }
    public Provider Provider { get; set; }
    // Granted access token for talking to the provider API on user's behalf.
    public string AccessToken { get; set; }
    // User's unique ID at the social provider.
    public string ProviderId { get; set; }

    // The user that this SocialProvider belongs to.
    public virtual User User { get; set; }
    // The users that have this social provider as a contact.
    public virtual ICollection<User> Contacts { get; set; }
}

The workflow is as follows:

1. I sign up within the application. This creates a User .
2. I attach social providers (Google, Facebook, etc). This creates one or more SocialProvider and adds it to user.SocialProviders .
3. I import my contacts/friends from my attached social providers. This pulls down a list of social contacts and creates a SocialProvider for each one if it does not already exist and adds them to user.SocialContacts . In this case the SocialProvider will not have a parent user that "owns" it, nor will it have an AccessToken until a user signs up with the application and adds a social provider that matches it, in which case those things will be populated.

Will this work? I have a feeling EF is about to get very confused. I'm not very familiar with the fluent API or even most of the data annotations. Any suggestions for what I can do to make this work, or should I just make SocialContacts be a new entity called SocialContact that mostly looks like SocialProvider just to avoid any confusing relationship stuff?

Answer 1

Try this:

User

public class User
{
   public int Id { get; set; }
   ublic string Password { get; set; }
   public string Name { get; set; }

   // Collection that represent this user's attached social providers.
   public virtual ICollection<SocialProvider> SocialProviders { get; set; }

   // Collection representing this user's friends from her attached social providers.
   public virtual ICollection<SocialProvider> SocialContacts { get; set; }
}

SocialProvider

public class SocialProvider
{
   public int Id { get; set; }        

   public string AccessToken { get; set; }       

   [ForeignKey("Provider"), DatabaseGenerated(DatabaseGeneratedOption.None)]
   public string ProviderId { get; set; }

   public Provider Provider { get; set; }

   [ForeignKey("User"), DatabaseGenerated(DatabaseGeneratedOption.None)]
   public string UserId { get; set; }

   // The user that this SocialProvider belongs to.
   public virtual User User { get; set; }

   // The users that have this social provider as a contact.
   public virtual ICollection<User> Contacts { get; set; }
}

Then in your DbContext class

protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<User>()
          .HasMany<SocialProvider>(r => r.SocialContacts)
          .WithMany(u => u.Contacts)
          .Map(m =>
          {
              m.ToTable("UsersInSocialContacts");
              m.MapLeftKey("UserId");
              m.MapRightKey("ProviderId");//If not ProviderId  try Id
          });
    }

I can't and haven't test this, so let me know the results so i can improve it. Ideally, you may have to pick this design apart and restructure it into one or more entities.