What is output from the following code snippet?

    int a = 10;
    int? b = null;
    int c = 20;

    Console.Write(a + (b ?? c));

The ?? is a null coalescing operator, if b is null then use c else use b, so for the snippet in the code the sum carried out is actually a + c as b is set to null, if b had a int value then the sum would have been a + b.