Entity Framework query across multiple levels of relationship

Question

I'm just beginning in Entity Framework and Linq To Entities and am trying to get my head around querying.

I have a data structure as follows:

Tables A, B, C.

A has one to many relationship to B, B has one to many relationship to C.

One of our presentation objects is composed of data from A, B & C given the Id from C

So, how can I represent this in a query?

How do I get an A entity from a where c.Id == myParam query?

Answer 1

What about:

var c = context.Cs.Include("B.A").Where(c => c.Id == myParam).SingleOrDefault();

Where B is navigation property on C to instance of B an A is navigation property from B to instance of A.

You can also use lambda notation if System.Data.Entity namespace is refeneced:

var c = context.Cs.Include(i=>i.B.A).Where(c => c.Id == myParam).SingleOrDefault();

And for Collection navigation properties you can use .Select()

var c = context.Cs.Include(i=>i.Select(j=>j.A)).Where(c => c.Id == myParam).SingleOrDefault();

Answer 2

the below works if you are making sure that all references of object A are loaded so you can access them.

var C= lstA.Where(p => p.B.FirstOrDefault().C == cID);