// Ex9_19.cpp : main project file.
  // Defining, triggering and handling events.
  include <stdafx.h>
  
  using namespace System;
  
  public delegate void DoorHandler(String^ str);
  
  // Class with an event member
  public ref class Door
  {
  public:
    // An event that will call functions associated
    // with an DoorHandler delegate object
    event DoorHandler^ Knock;      
  
    // Function to trigger events
    void TriggerEvents()
    {
      Knock(L"Fred");
      Knock(L"Jane");
    }
  };
  
  // Class defining handler functions for Knock events
  public ref class AnswerDoor
  {
  public:
    void ImIn(String^ name)
    {
      Console::WriteLine(L"Come in {0}, it's open.",name);
    }
  
    void ImOut(String^ name)
    {
      Console::WriteLine(L"Go away {0}, I'm out.",name);
    }
  };
  
  int main(array<System::String ^> ^args)
  {
    Door^ door = gcnew Door;
    AnswerDoor^ answer = gcnew AnswerDoor;
  
    // Add handler for Knock event member of door
    door->Knock += gcnew DoorHandler(answer, &AnswerDoor::ImIn);
  
    door->TriggerEvents();               // Trigger Knock events
  
    // Change the way a knock is dealt with
    door->Knock -= gcnew DoorHandler(answer, &AnswerDoor::ImIn);
    door->Knock += gcnew DoorHandler(answer, &AnswerDoor::ImOut);
    door->TriggerEvents();               // Trigger Knock events
    return 0;
  }