Explain how related data is loaded in Entity Framework and how it differs from lazy loading.

In Entity Framework, loading related data can be done in two main ways:

1. Eager Loading — related data is loaded immediately along with the main data when executing the query. This is done using the Include method.

var orders = context.Orders.Include(o => o.Customer).ToList();

In this example, related customer data is loaded along with the orders.

2. Lazy Loading — related data is loaded only when first accessed in the code, i.e., deferred. This requires proxy setup and virtual navigation properties.

var order = context.Orders.First();
var customerName = order.Customer.Name; // A separate database query occurs here

Differences:

• Eager loading executes all necessary queries at once, reducing database calls but potentially loading unnecessary data.
• Lazy loading conserves resources by loading data as needed but can lead to multiple separate queries (N+1 problem).

The choice of approach depends on the scenario and performance requirements.