How to include correctly property within a collection when using Entity Framework code first

Posted on: 2013-05-10

I have several examples in this website that include with a string the property when it's a property inside a collection of my main entity. Here is one example:

 return DatabaseContext
 .SetOwnable<Workout>()
 .Include(x => x.Sessions)
 .Include("Sessions.WorkoutSessionExercises")
 .Include("Sessions.WorkoutSessionExercises.Exercise")
 .Single(c => c.Id == id); 

At least, this example use the property for the Sessions. But why I wrote with a string for the two others includes? Because Sessions is a collection which doesn't let me link to one of its property. Instead, it links me to a list of property of the collection. This is quite logic if we think about it. However, I remain with the problem of using string which will lead in the maintenance phase to some possible problem when refactoring. Renaming a property won't change the string. This is why it would be better to specify the property of the collection.

This can be done by using the Linq method "Select".

 return DatabaseContext
 .SetOwnable<Workout>()
 .Include(x => x.Sessions)
 .Include(x => x.Sessions.Select(d=>d.WorkoutSessionExercises))
 .Include(x => x.Sessions.Select(d=>d.WorkoutSessionExercises.Select(g=>g.Exercise)))
 .Single(c => c.Id == id); 

As you can see, we load the collection Sessions, then we load the collection WorkoutSessionExercise which is inside every Session. Finally, we load every Exercise that is a property without being a collection.

This example show you that even with multiple collection deep you can still avoid using string to specify that to include and what not.