freeCodeCamp/guide/english/csharp/null-conditional-operator/index.md

title
Null-conditional Operator

Null-conditional Operator

Null-conditional operators allow for null checking with a minimal amount of code. For example, if you had an employee variable of type Employee with a property of type Address, you might do null checking as follows:

Address address = null;
if (employee != null)
{
    address = employee.Address;
}

You could use a standard conditional operator to make that check more concise:

Address address = employee != null ? employee.Address : null;

However, in C# 6.0 null-conditional operators were introduced, so now the above line can simply be represented as follows:

Address address = student?.Address;

If employee is null, address will simply be assigned null, and no NullReferenceExeception will occur. This becomes more useful with deeper object graphs, as you can handle a chain of conditional member access.

For example:

string city = student?.Address?.City;

Null-conditional operators are short-circuiting, so as soon as one check of conditional member access returns null, the rest do not take place.

Null-coalescing operator

Another useful null-checking option is the null-coalescing operator. It returns the left-hand operand if the operand is not null; otherwise it returns the right hand operand.

For example:

public string GetStringValue()
{
    return null;
}

// Display the value of s if s is NOT null. If x IS null, display the string "It was null."

string x = GetStringValue();

Console.WriteLine(x ?? "It was null.");

// Result:

"It was null."