C# Language Null-Conditional Operator

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The ?. operator is syntactic sugar to avoid verbose null checks. It's also known as the Safe navigation operator.

Class used in the following example:

public class Person
    public int Age { get; set; }
    public string Name { get; set; }
    public Person Spouse { get; set; }

If an object is potentially null (such as a function that returns a reference type) the object must first be checked for null to prevent a possible NullReferenceException. Without the null-conditional operator, this would look like:

Person person = GetPerson();

int? age = null;
if (person != null)
    age = person.Age;

The same example using the null-conditional operator:

Person person = GetPerson();

var age = person?.Age;    // 'age' will be of type 'int?', even if 'person' is not null

Chaining the Operator

The null-conditional operator can be combined on the members and sub-members of an object.

// Will be null if either `person` or `person.Spouse` are null
int? spouseAge = person?.Spouse?.Age;

Combining with the Null-Coalescing Operator

The null-conditional operator can be combined with the null-coalescing operator to provide a default value:

// spouseDisplayName will be "N/A" if person, Spouse, or Name is null
var spouseDisplayName = person?.Spouse?.Name ?? "N/A";
Null-conditional Operator can be used with Extension Method