C# 6 > Null-Conditional Operator

One of the useful additions to the C# language in version 6 that I regularly use is the null-conditional operator. Checking for null is something that is regularly done, the new null-conditional operator helps to reduce the amount of code that you have to write.

Below is a simplified explanation of the null conditional operator:

The expression A?.B evaluates to B if the left operand 'A' is not null; otherwise, it evaluates to null.

Here’s a simple example of how it can be used.

public class Dog
{
    public string Name { get; set; }
    public int Age { get; set; }
    public Toy FavouriteToy { get; set; }
}

Assume that d represents a dog. We can do the following.

var name = d?.Name;
var breed = d?.Breed;

The variable name is a string. If d is null, name is null. If d is not null, name is the value of d.Name.

The variable age is an nullable int. If d is null, age is null. If d is not null, age is the value of d.Age.

Consider the example above where the Dog class contains a reference to the dog’s favourite toy. We can chain null-conditional operators to retrieve the favourite toy’s name.

var favouriteToy = d?.FavouriteToy?.Name;

This is roughly equivalent to

var favouriteToy = (d == null) ? null : (d.FavouriteToy == null) ? null : d.FavouriteToy.Name;

So we can see in this example the code becomes a lot cleaner.

Other usage scenarios

GetDog()?.FavouriteToy?.Name ?? "Dog needs a name";

private Func<Dog, bool> Walk;

Walk?.Invoke(dog)

var thing = new TFoo();

(thing as ICanDoSomething)?.DoSomething();