EF 4.1 Code First. Table-per-type inheritance with different primary key name from its base class' primary key name

Question

Given this:

create table Location(
LocationId int identity(1,1) not null primary key,
Address nvarchar(max) not null,
City nvarchar(max) null,
State nvarchar(max) not null,
ZipCode nvarchar(max) not null
);



create table Park(
ParkId int not null primary key references Location(LocationId),
Name nvarchar(max) not null
);

I tried this mapping:

modelBuilder.Entity<Location>();
modelBuilder.Entity<Park>().ToTable("Park");
modelBuilder.Entity<Park>().Property(x => x.LocationId).HasColumnName("ParkId");

Unfortunately that didn't work.

using (var db = new Ef())
{
    var park = new Park { Name = "11th Street Park", Address = "801 11th Street", City = "Aledo", State = "TX", ZipCode = "76106" };
    db.Set<Location>().Add(park);

    db.SaveChanges();
}

It has this error:

The property 'LocationId' is not a declared property on type 'Park'. Verify that the property has not been explicitly excluded from the model by using the Ignore method or NotMappedAttribute data annotation. Make sure that it is a valid primitive property.

How should I map Park entity so its LocationId property fall to ParkId column?

I have this mapping by the way:

public class Location
{
    public virtual int LocationId { get; set; }
    public virtual string Address { get; set; }
    public virtual string City { get; set; }
    public virtual string State { get; set; }
    public virtual string ZipCode { get; set; }
}

public class Park : Location
{
    public virtual string Name { get; set; }
}

If it could help, this is possible in EF 4.0 (via designer), just followed the steps in Chapter 2-11 of Entity Framework 4.0 Recipes, Problem Solution Approach. Now I'm trying it on code first via EF 4.1

[EDIT]

If I change the ParkId to LocationId, things are ok. However, with designer approach, it is possible to map the LocationId to ParkId of table Park; I want to achieve the same thing with code first

create table Park( 
LocationId int not null primary key references Location(LocationId), 
Name nvarchar(max) not null 
); 

Answer 1

As I know (and I tried it multiple times) code first doesn't support this => your derived type should use same column names for primary key.

This problem can be described very simply: Current fluent mapping implementation doesn't allow overriding mapping rules from parent entity => parent entity defines names of primary key columns in all derived entities.

IMO the most probable reason is that it was really designed as code first where you don't have existing database and you do not have to bother with database naming - it was up to EF to define names as it needed. Once DbContext API was released people started to use it with existing database massively. But here comes a problem: Initial use cases didn't count with this so some scenarios which are pretty easily done in EDMX are not possible. This is one of them.

Answer 2

Here is a workaround for this issue:

Create a view for the derived table and map your entity class that view. Rename the key column in your view so that it matches the key column in the base table.

eg:

base table User (UserID, FirstName, LastName)

derived table Manager (ManagerID, DepartmentID)

Entity Framework fails to update Manager as the key column is different!

solution:

create view UserManager
as
select
ManagerID as UserID,
DepartmentID
from Manager

Then map the Manager class to the UserManager view, instead of to the Manager table.