//public static void changNumber(AB a)
 public void changNumber(AB ob)
 {
     Console.WriteLine("Inside Method Call Before Modification, Number = " + ob.number);
     ob.number = 500;
     Console.WriteLine("Inside Method Call After Modification, Number = " + ob.number);
     ob = null;
     // ob = obj2;
     Console.WriteLine("Inside Method Call when ob = NULL, Number = " + ob);
 }
        public static void Main()
        {
            AB ob1 = new AB();

            ob1.number = 34;
            Console.WriteLine("Before Method Call Number = " + ob1.number);

            CD obj2 = new CD();

            //CD.changNumber(ob1) ;
            obj2.changNumber(ob1);
            Console.WriteLine("After Method Call Number = " + ob1.number);
        }