|The value to test for null value. If non null, this value is returned. Must be a nullable type.|
|The value returned if |
The null coalescing operator itself is two consecutive question mark characters:
It is a shorthand for the conditional expression:
possibleNullObject != null ? possibleNullObject : defaultValue
The left-side operand (object being tested) must be a nullable value type or reference type, or a compile error will occur.
The ?? operator works for both reference types and value types.