EF - Eager include grandchildren not working, does not contain definition for 'Select' - entity-framework

Question

I am working in VS 2015 solution with an MVC 5 project and a code library project using EF 6.1. I have redone the entire project from a previous version in VS 2013 hoping it would resolve this problem, but no luck. I am just trying to eager load a child with grandchildren. I tried this:
Test t = db.Tests
.Include("TestsRemoteOBD")
.Include("TestsRemoteOBD.TestsRemoteOBDDtcs")
.FirstOrDefault();
and this:
Test t = db.Tests
.Include(i=>i.TestsRemoteOBD)
.Include(i=>i.TestsRemoteOBD.Select(s=>s.TestsRemoteOBDDtcs))
.FirstOrDefault();
Include using the string works for the child, but not the grandchildren. And with the 2nd query, I'm getting this error:
'TestsRemoteOBD' does not contain a definition for 'Select' and no extension method 'Select' accepting a first argument of type 'TestsRemoteOBD' could be found (are you missing a using directive or an assembly reference?)
I've seen the same question resolved by adding "using System.Data.Entity;", but I had done that a long time ago. No help. What else could I be missing?
Thanks!

Answer 1

Thanks so much, to all those who commented. I would have been banging my head for another day, at least. The way I had written the second statement would have worked fine if the parent [Tests] had a 1-to-many relationship with [TestRemoteOBD], but since the latter was not a collection, there was no 'Select' defined. I have not tested, but I believe it should be something like:
Test t = db.Tests
.Include(i=>i.TestsRemoteOBD)
.Include(i=>i.TestsRemoteOBD.TestsRemoteOBDDtcs)
.FirstOrDefault();

Answer 2

Bump. Found this and thought I'd throw in my own research.
Microsoft's
Documentation
states: To include a reference and then a reference one level down: query.Include(e => e.Level1Reference.Level2Reference)
-- but this doesn't seem to work under even the simplest use case. Executing the query with a .ToList() does not actually include anything. Smells like an obvious bug to me!
I can see 2 workarounds.
First, as Ben here suggests, you can manually iterate over the entities to force EF to load them.
Second, if scoping permits, you can forget the 'using' block and keep a more permanent instance of the dbcontext as a class member so that it's still available, not disposed (System.ObjectDisposedException), when the members are accessed.