option

It is a very common pattern to return null when something does not exist. Suppose we have a system where a UserRepository object can retrieve User objects from persistent storage - like a database. public class UserRepository { public User Get(string email) => context.Users.SingleOrDefault(u => u.Email == email); /* ... */ } This is also a very common source of bugs. Consumers of the UserRepository routinely forget to check whether the reference returned is null, causing the code to blow up at runtime unexpectedly....