What is N+1 query problem in Entity Framework and how to fix it?

The N+1 query problem is a common performance issue in Entity Framework. It occurs when the application makes multiple database queries to retrieve related data for each record returned by the initial query. This can lead to a significant increase in the number of database queries and slow down the application.

To fix this problem, you can use eager loading or lazy loading. Eager loading retrieves all related data in a single query, while lazy loading retrieves related data only when it is accessed for the first time. You can also use explicit loading to load related data on demand.

Here is an example of how to use eager loading with Orders in Entity Framework:

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

This code retrieves all orders and their associated customers in a single query.