If you are reviewing a C# code and you've come across a double question mark operator (??), you must be wondering what this double question mark operator do in C#.

In this blog post, we will learn what this double question mark operator does and we will also see a few usages of this operator in some code examples.

 

 

 

 

Null Coalescing Operator C# - Double Question Mark Operator In C# (?? in C#)

The double question mark operator also called the null coalescing opertor in C#.

The null coalescing operator returns the value of its left-hand operand if it isn't null.

Otherwise, it evaluates the right-hand operand and returns its result.

Let's look at a practical code example and understand more about the Double Question Mark Operator or null coalescing operator.

string name = null; // some other code var checkName = name ?? "Name is null"; // Display Console.WriteLine(checkName);

 

Result:

Name is null

 

In the same code example, if the name field was not null, then checkName would have been evaluated to the value of the name field.

string name = null; // some other code name = "John Doe"; var checkName = name ?? "Name is null"; // Display Console.WriteLine(checkName);

 

Result:

John Doe