Cannot define keys on type 'User' deriving from 'People'. Only the root type in the entity inheritance hierarchy can contain keys

Question

I am using Web API 2.2 project with OData4 package + Entity Framework 6.

I have a User class which inherits from People class. People class itself inherits from Person class.

[Table("People")]
public class People : Person
{ }

public class User: People
{
   [Key]
   public int UserId { get; set; }
   [ForeignKey("Anonymous")]
   public int AnonymousId { get; set; }
}

When I execute the code an exception is thrown in WebApiConfig::Register method on this line

config.MapODataServiceRoute(
        routeName: "ODataRoute",
        routePrefix: null,
        model: builder.GetEdmModel());

Error:

An exception of type 'System.InvalidOperationException' occurred in System.Web.OData.dll but was not handled in user code

Additional information: Cannot define keys on type 'User' deriving from 'People'. Only the root type in the entity inheritance hierarchy can contain keys.

I have tried solution given at http://stack247.wordpress.com/2013/02/28/cannot-define-keys-on-type-deriving-from-only-root-type-in-entity-inheritance-hierarchy-can-contain-keys/

but it did not work.

I tried :

builder.EntityType<User>().DerivesFrom<People>();
builder.EntityType<People>().DerivesFrom<Element>();

Answer 1

As suggested by Gert we have removed key attribute from child class.
This has resolved the problem.