Demanding honesty from function inputs

A truly robust system is not just about what you return; it’s also about what you accept. Guarding your functions against potentially misleading or harmful inputs is paramount in creating predictable, error-resistant applications.

Consider this common scenario: You have a function that expects a certain type of input. However, when a null value sneaks its way in, your function breaks down, leading to the infamous NullReferenceException. To mitigate this, C# provides a way to demand honesty from function inputs using nullable reference types.

Let’s say you define a function as follows:

public void UpdateUserProfile(UserProfile profile)
{
    // Some operations on profile
}

The intention is clear: the function expects UserProfile. However, what’s stopping a developer from passing in null?

Nullable reference types to the rescue

As we discussed earlier, with C# 8.0, nullable reference types...