Null parameter checking in C#

Question

In C#, are there any good reasons (other than a better error message) for adding parameter null checks to every function where null is not a valid value? Obviously, the code tha

Answer 1

int i = Age ?? 0;

So for your example:

if (age == null || age == 0)

Or:

if (age.GetValueOrDefault(0) == 0)

Or:

if ((age ?? 0) == 0)

Or ternary:

int i = age.HasValue ? age.Value : 0;