Exercise: Refactoring a Function to Prevent Null

Preventing a NullReferenceException

Now, let’s play!

Let’s refactor a method that throws a NullReferenceException. For this exercise, we’ll continue working with a catalog of movies. This time, each movie contains a director and some reviews. Each review has a score and a comment.

When working with collections, we can prevent a NullReferenceException by always initializing collections before using them. For example, before trying to add an element to a list, we should initialize it to an empty list.

To complete this exercise, add null checks, initialize collections, and use ArgumentNullException where appropriate to prevent a NullReferenceException.

Follow the instructions in the comments to complete this exercise.