Entity Framework Multi-level Inheritance with TPH

Question

I am working with a legacy system that implements a TPH for a certain number of items. So the current structure looks like this

 Abstract Class 1     Abstract Class 2     Abstract Class 3
         |                    |                    |
     ---------            ---------            ---------
    |    |    |          |    |    |          |    |    |
    T1   T2   T3        T4    T5   T6         T7   T8   T9

So Type (T*) is a discriminator across all tables but since certain types share common columns, there are a significant number of different tables. The problem is that all of these items actually share a small commonality but there is no way to gather all of these items into a collection. In reality the hierarchy actually should look more like this.

          --------------- Base Abstract 1 ---------- 
         |                    |                    |
 Abstract Class 1     Abstract Class 2     Abstract Class 3
         |                    |                    |
     ---------            ---------            ---------
    |    |    |          |    |    |          |    |    |
    T1   T2   T3        T4    T5   T6         T7   T8   T9

So essentially what we have is a TPT where each Table per type is a TPH. For a real world example, here is what we need.

          ---------------  Vehicle   --------------- 
         |                    |                    |
        Car                 Boat                 Plane
         |                    |                    |
     ---------            ---------            ---------
    |    |    |          |    |    |          |    |    |
   BMW Toyota Fiat      T4   T5   T6         T7    T8   T9

Obviously there are some design flaws with the initial design and no one anticipated needing to grab a list of all vehicles without querying 3 different tables. So my question is, with the existing structure is there a way add this new hierarchy to entity framework. I was thinking something like this

  Vehicle
  -------
  VehicleId
  TypeId (Boat, Plane, Car, etc)
  ItemFK (BoatID, PlaneId, CarId)

Is this possible? Is there a way to map these in entity framework? I cant seem to match them correctly. It seems it could possibly work if we were to replace BoatId, PlaneId, and CarId with VehicleId (like Conditional Mapping in Entity Framework - OR operation with TPH) but at that point we would be doing a really invasive schema change which is not really an option and I'm not sure that would even work. Essentially I need a way to map existing keys into a new hierarchy. Any help is greatly appreciated. I'm at a loss and can't seem to find any solution that answers my question.

Answer 1

You could use this structure

 public class Vehicle
    {
        [Key]
        public int Id { set; get; }

        ///
        // common properties
        ///

        public Car Car { set; get; }
        public Boat Boat { set; get; }
        public Plane Plane { set; get; }
    }

    public class Car
    {
        [Key, ForeignKey("Vehicle")]
        public int VehicleId { set; get; }
        public Vehicle Vehicle { set; get; }

        ///
        // Car properties
        ///
    }

    public class Boat
    {
        [Key, ForeignKey("Vehicle")]
        public int VehicleId { set; get; }
        public Vehicle Vehicle { set; get; }

        ///
        // Boat properties
        ///
    }

    public class Plane
    {
        [Key, ForeignKey("Vehicle")]
        public int VehicleId { set; get; }
        public Vehicle Vehicle { set; get; }

        ///
        // Plane properties
        ///
    }