c# - How to handle null if passed from a calling function to a called function whose parameter is nullable integer? -

i have been asked question in interview

public int add(int? a, int? b) {     return a+b; }

null passed in a's place. how handle this?

i said

if (a == null ) { //do } else { // }

he didnot anything.

waiting reply.

whtever have said correct interviewer might wanted know how updated are..

 if(!a.hasvalue)     {         = 0;     }

or shorter :-

a = != null ? : 0;

and 1 more operator suggested askolein ?? shown below :-

a ?? 0;

Deter