Does First() in LINQ cause eager or lazy loading?

Question

I have a query:

db.Order.Include("OrderItem").First(r => r.Id == OrderId)

1. Does First() on it own cause Eager or Lazy loading?
2. If not then how would you force Eager loading for a First()?
3. Is the above combined query Eagerly or lazily loaded?

Answer 1

First() and FirstOrDefault() are executed immediately (eager) at the point where they're called.

All standard LINQ operators, which return a single, non-enumerable result, and those that do not return an explicit IEnumerable<T>, are executed immediately.

See Classification of Standard Query Operators by Manner of Execution for the complete list of LINQ operators.