private void PersonRef()
 {
     Person john = new Person("John", 65);
      john.Display();
      SetPersonByValue( john );
      john.Display();
      SetPersonByRef(ref john);
      john.Display();
 }
 private void SetPersonByValue(Person person)
 {
     person.Age = 99;
      person = new Person( "Nikki", 99 );
 }
 private void SetPersonByRef( ref Person person)
 {
     person.Age = 88;
      person = new Person( "Nikki", 22 );
 }