How do I check to see if Variable....int

I am learning C# and need some help with my code:
I have a code below and need to validate that the variable has a int value or not, how do I accomplish this task?
Goal: When a int is passed through my static method, how do I check for a int value.  If int InputValue is NULL I need to return nothing, if the value has a int Data, I need to return that int value -- Your help is greatly needed and apprieciated thank you.