Mapping Uni-directional Relationships with EF Code First

Question

I'm fairly new to EF Code First and this may (hopefully!) be a simple question.

I have a simple relationship between People and Address:

People
------
PersonID
Name

Address
-------
AddressID
Address1
PersonID

Most times I've had AddressID in my People table; but this db is a bit "backwards", in that it references the PersonID. In my code, I deal with Person objects and want to get their associated Address. The relationship could be 1 person having many addresses, but it's always 1:1. (This is a 3rd party DB - I can't control the schema.)

How would I set up the relationships in Code First to associate Person and Address? I'm using the fluent API, but I don't see a way to set it up without having a key in both entities. Ideally, I would like my entities to be set up like:

Person { 
 public int PersonID {get;set;}
 public string Name {get;set;}
 //other person properites

 //navigation property
 public Address Address {get;set;}
}

Address {
 public string Address1 {get;set;}
 //other properties for address

 //navigation property
 public Person Person {get;set;}
}

I've tried a few ways to configure the relationship, but it keeps erroring out. I've tried defining the Address class as a complex type, but since it's a separate table, can that work? Also, I've tried using the HasOptional and WithOptionalDependant, but to no avail.

So any thoughts on how to best configure my EF CF logic to allow Address to be an entity within Person.

Any suggestions or help is greatly appreciated.

UPDATE I tried Mark's suggestion below, but I'm getting a different error. (See my comment)

My Address entity setup sets PersonID as the entity key:

modelBuilder.Entity<Address>()
 .HasKey(a => a.PersonID);

modelBuilder.Entity<Address>()
 .Property(a => a.PersonID)
 .HasColumnName(<my real column name>);

So the entity's key in the DB is PersonID, but it's also a FK back to Person. Is this causing the problem? (Again, not my DB - it's a 3rd party.) Any help is greatly appreciated. Thanks!!

Answer 1

Are you sure you're wanting a 1:1 relationship?

The relationship could be 1 person having many addresses, but it's always 1:1. (This is a 3rd party DB - I can't control the schema.)

This implies that you actually want a 1:many relationship correct?

That being said, I think a navigation collection would be the ideal way to map Address(es) to the Person Object:

Person { 
 public int PersonID {get;set;}
 public string Name {get;set;}
 //other person properites

 //navigation property
 public virtual ICollection<Address> Addresses {get;set;}
}

And here's the corresponding Fluent (this assumes that you have a PersonID mapped into address, which you do when you describe the DB, but not in your code)

modelBuilder.Entity<Person>()
            .HasMany(p => p.Addresses)
            .WithRequired(a => a.Person)
            .HasForeignKey(a => a.PersonID);

Answer 2

I figured it out going off the suggestion from Mark.

modelBuilder.Entity<Person>()
  .HasOptional<Address>(p => p.Address)
  .WithRequired(a => a.Person);

I need to set up an optional:required mapping, since a Person may not have an Address (not likely, but I guess it's possible), but an Address has a Person since the PK of Address is the PersonID.

The key to watch out for is a circular reference between Person and Address when serializing the results (I caught this in my controller when serializing the results to JSON). I got around this by disabling proxy creation on the context for my specific query(ies) where I'm getting person-address information:

_context.Configuration.ProxyCreationEnabled = false;

Once I did that, I use Lazy Loading to get my Address information off Person when I need it, and it all works. Thanks for the help all!