?? operator (C#)

The ?? operator returns the left-hand operand if it is not null, or else it returns the right operand. For example:

int? x = null;

...

// y = x, unless x is null, in which case y = -1.

int y = x ?? -1;

The ?? operator also works with reference types:

//message = param, unless param is null

//in which case message = "No message"

string message = param ?? "No message";