Chain of Responsibility Design Pattern in C#

Avoids coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it.

This structural code demonstrates the Chain of Responsibility pattern in which several linked objects (the Chain) are offered the opportunity to respond to a request or hand it off to the object next in line.

using System;

  class MainApp
  {
    static void Main()
    {
      // Setup Chain of Responsibility 
      Handler h1 = new ConcreteHandler1();
      Handler h2 = new ConcreteHandler2();
      Handler h3 = new ConcreteHandler3();
      h1.SetSuccessor(h2);
      h2.SetSuccessor(h3);

      // Generate and process request 
      int[] requests = {2, 5, 14, 22, 18, 3, 27, 20};

      foreach (int request in requests)
      {
        h1.HandleRequest(request);
      }

      // Wait for user 
      Console.Read();
    }
  }

  // "Handler" 
  abstract class Handler 
  {
    protected Handler successor;

    public void SetSuccessor(Handler successor)
    {
      this.successor = successor;
    }

    public abstract void HandleRequest(int request);
  }

  // "ConcreteHandler1" 
  class ConcreteHandler1 : Handler
  {
    public override void HandleRequest(int request)
    {
      if (request >= 0 && request < 10)
      {
        Console.WriteLine("{0} handled request {1}", 
          this.GetType().Name, request);
      }
      else if (successor != null)
      {
        successor.HandleRequest(request);
      }
    }
  }

  // "ConcreteHandler2" 
  class ConcreteHandler2 : Handler
  {
    public override void HandleRequest(int request)
    {
      if (request >= 10 && request < 20)
      {
        Console.WriteLine("{0} handled request {1}", 
          this.GetType().Name, request);
      }
      else if (successor != null)
      {
        successor.HandleRequest(request);
      }
    }
  }

  // "ConcreteHandler3" 
  class ConcreteHandler3 : Handler
  {
    public override void HandleRequest(int request)
    {
      if (request >= 20 && request < 30)
      {
        Console.WriteLine("{0} handled request {1}", 
          this.GetType().Name, request);
      }
      else if (successor != null)
      {
        successor.HandleRequest(request);
      }
    }
  }