Double Question Mark in C#

This article will introduce double question mark meaning in C#.

Use the ?? Operator as a Null Coalescing Operator in C#

We use the ?? operator as a null coalescing operator in C#. It returns the value of its left-hand operand if it isn’t null. If it is null, then it evaluates the right-hand operand and returns its result. The ?? operator does not evaluate its right-hand operand if the left-hand operand evaluates to non-null. The correct syntax to use this symbol is as follows.

A ?? B

In the above example, B is returned if A is null.

The program below shows how we can use the null coalescing operator.

using System;
public class Program {
  public static void Main() {
    int? a = null;
    int b = a ?? 10;
    Console.WriteLine(b);
  }
}

Output:

10

In the above code, we can see that the value of b is 10 as a is null.