Retrieve only base class from Entity Framework

Question

If I have three classes in entity framework.

class Base {}

class Left : Base {}

class Right : Base {}

and I call DBContext.Bases.ToList();

This returns all instances of Base fully typed into their associated inherited types, as some people have noticed, the performance of EF on large inheritance structures is not great to say the least. My actual query in my project is 600 lines long, just for returning one entity and takes 2 seconds to generate.

They query runs much faster if you tell it which type to return, as it does not have to join across the whole structure. e.g.

DBContext.Bases.OfType<Left>.ToList();
or
DBContext.Bases.OfType<Right>.ToList();

However I now want to ONLY return the base class. Unfortunalty doing

DBContext.Bases.OfType<Base>.ToList(); 

does the same as DBContext.Bases.ToList();

It gets the WHOLE inheritance structure... Is there any way (without making a new type in EF) of ONLY returning the class Base when looking through the Base collection?

Answer 1

Assuming you are able to use LINQ, could you use something along the lines of the following quick and dirty example?:

var result = from item in DBContext.Bases.ToList()
            where (!item.GetType().IsSubclassOf(typeof(Base)))
           select item;

Answer 2

This is, unfortunately, harder than you might expect, at least in LINQ to Entities. In Entity SQL you can use OFTYPE(ONLY...). Alex James explains how to do it in this tip.

Answer 3

Sorry I cant log into my actual account...

Maybe I didnt make myself clear, I want to bring back all the objects (including Base, Left and Right) but I only want the Base class to be returned, even if in the database they are actual Left and Right classes.

OFTYPE was a good suggestion but it filters out all my entities because none are the actual Base type. But I want to return only the Base type values in the Base type object.

Any ideas?