uses the reference parameter of a multicast delegate as a counter : Multi cast delegate : Delegate C# Examples

    
using  System;

public  delegate  void  DelegateClass(int  valCount,  ref  int  refCount);

public  class  Counter  {
        public  static  void  Main()  {
                DelegateClass  del  =  (DelegateClass)AddOne  +  (DelegateClass)AddTwo  +  (DelegateClass)AddOne;
                int  valCount  =  0;
                int  refCount  =  0;
                del(valCount,  ref  refCount);
                Console.WriteLine("Value  count  =  {0}",  valCount);  //  0
                Console.WriteLine("Reference  count  =  {0}",refCount);  //  4
        }

        public  static  void  AddOne(int  valCount,ref  int  refCount)  {
                ++valCount;
                ++refCount;
        }

        public  static  void  AddTwo(int  valCount,ref  int  refCount)  {
                valCount  +=  2;
                refCount  +=  2;
        }
}