c# - EntityFramework Include (Eager Load) virtual Property of virtual property -

imagine have 3 dbsets below:

category { ...    public virtual icollection<item> items {get; set;} ... }  item { ...    public virtual icollection<specification> specifications{get; set;} ... }  specification { ... } 

for eager loading use this:

category cat = db.categories.include(c=> c.items).firstordefault(c=> c.id == 1); 

but problem

cat.items[0].specifications null, how can make eager load sub collections of collection too?

p.s.: tried removing virtual keyword testing (i'm don't want remove it) didn't work either.

you can use notation

db.categories.include("items.specifications") 

note has string