EF Eager fetching derived class

Question

I´m using EF6 and trying to eager fetch the whole structure of an object. The problem is that i´m using inheritance.

Let´s say that i have this classes.

Answer 1

Your problem is not in the Select(y=>y.SomeClass) it self, if you try to remove it from your query and execute your query again, you will get same problem. You cannot query the inherited type as child and you expect from entity framework to take care for everything.

If you look to your database, the table Base has a reference to A which is relation 1-many from A to Base.

you can either get all the Base entities where A.Id = something, by adding a navigational property A in the class Base, and in your DbContext you add DbSet Bases{get;set;} then your query will look like this

var details = _ctx.Bases.OfType()
                        .Include(t=>t.Box)
                        .Include(t=>t.SomeClass)
                        .Where(t=>t.Box.Id ==something);

Other option, to use a DTO, in the below sample I used Anonymous type, but you can create a strongly DTO typed to meet your requirements.

var details  = _ctx.A
                   .Where (t=>t.Id ==something)
                   .Select(a => new {
                        Id = a.Id,
                        // ... other A properites , 
                        Bases = _ctx.Bases.OfType().Select(m=> new {
                            Id = m.Id,
                            Name = m.Name,
                            SomeClass = m.SomeClass
                        });
                   }

Hope this will help you