c# - how to use eager loading without string for related entities? -

i use eager loading load related entities , see this page:

in example can see there 2 ways related entities:

var princesses1 = context.princesses                           .include(p => p.unicorns)                           .tolist();   var princesses1 = context.princesses                           .include("unicorns")                           .tolist(); 

the first way use lambda expression (i think correct name that, if not, correct me), , second way use string name of related entity.

in case, can use second, because in firt way, when can't property of related entity in lambda expression. use code:

iqueryable<customers> myquery; myquery = mycontext.customers.include("orders"); 

but if try use second way:

iqueryable<customers> myquery; myquery = mycontext.customers.include(c=>c.?????); 

i can't select orders property.

why?

add top of file:

using system.data.entity; 

this includes reference dbextensions class provides include extension method.