Check an integer value is Null in c#

Nullable<T> (or ?) exposes a HasValue flag to denote if a value is set or the item is null.

Also, nullable types support ==:

if (Age == null)

The ?? is the null coalescing operator and doesn't result in a boolean expression, but a value returned:

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;

Several things:

Age is not an integer - it is a nullable integer type. They are not the same. See the documentation for Nullable<T> on MSDN for details.

?? is the null coalesce operator, not the ternary operator (actually called the conditional operator).

To check if a nullable type has a value use HasValue, or check directly against null:

if(Age.HasValue)
{
   // Yay, it does!
}

if(Age == null)
{
   // It is null :(
}

There is already a correct answer from Adam, but you have another option to refactor your code:

if (Age.GetValueOrDefault() == 0)
{
    // it's null or 0
}