Question

I am trying to use code first with an existing db. So far it went well, but now I am failing at a one to many to one relationship.

There is a table customer and a table address in the db where address does NOT have any customerid but a foreign one to many key FK_Address_Customer.

The auto created classes from the edmx look like

Customer:

public int CustomerID (PK)
public Address Address

Address:

public int AddressID (PK)
public HashSet<Customer> Customers

Whatever I do in the fluent API either fails with invalid column Address_AddressID or Multiplicity conflicts with the referential constraint error.

I assumed:

//Customer has one address, address can have multiple customers<br/>
pModelBuilder.Entity<Customer>().HasRequired(m => m.Address).WithMany(x => x.Customers);


//Address has multiple customers, customer has one address<br/>
pModelBuilder.Entity<Address>().HasMany(m => m.Customers).WithRequired();

I got this correct on other tables where there where NO foreign keys in the db by using HasForeignKey, but in the above scenario it does not work. I also tried via MapKey passing the foreign key name also with no luck.

Ho do I get this simple relationship going ?

Thanks

Answer 1

You must tell EF the name of FK in Customer table otherwise it will use default Address_AddressID. HasForeignKey will do the magic.

pModelBuilder.Entity<Customer>()
             .HasRequired(c => c.Address)
             .WithMany(a => a.Customers)
             .HasForeignKey(c => c.AddressID);

Where AddressID is FK property in your Customer entity. If you don’t have FK property in the Customer entity you need to use Map:

pModelBuilder.Entity<Customer>()
             .HasRequired(c => c.Address)
             .WithMany(a => a.Customers)
             .Map(m => m.MapKey("AddressID"));

Where AddressID is a name of FK column in Customer table. You always need that column to have one-to-many relation.

The difference between having and not having FK property in your entity make difference between two types of associations supported by EF.