The purpose of Include() in ASP.NET MVC + Entity Framework

Question

In the controllers generated by Visual Studio, as well as the sample application (ContosoUniversity), the Index action always has something like

var departments = db.Departments.Include(d => d.Administrator);

What's the difference between that and

var departments = db.Departments;

First I suspected that the first one (with Include) enables the view to retrieve department.Administrator. But the second one (without Include) seems to be able to do that as well.

Answer 1

In first case (with Include) when you write department.Administrator servers the object from memory that has been eagerly loaded due to Include method. In the second case, an sql statement will be executed to fetch the Administrator record from the db for each department object.