Question

Please explain me what is different between this two statement.

first statement throw the exception and second one returns the Boolean value

Version a = null;

if(a.Equals(null)) // throw the exception

if(Equals(a,null)) // return the bool value true

Answer 1

You cannot call a.Equals without initializing a with an object, otherwise it will throw NullReferenceExcption, But Equals is a static method, it checks whether the two references passed to it are same or not, these references can have null values.