Chain of Responsibility

// Chain of Responsibility pattern -- Real World example

using System; namespace DoFactory.GangOfFour.Chain.RealWorld {    // MainApp test application    class MainApp   {      static void Main()     {        // Setup Chain of Responsibility       Director Larry = new Director();       VicePresident Sam = new VicePresident();       President Tammy = new President();       Larry.SetSuccessor(Sam);       Sam.SetSuccessor(Tammy);        // Generate and process purchase requests       Purchase p = new Purchase(2034, 350.00, "Supplies");       Larry.ProcessRequest(p);       p = new Purchase(2035, 32590.10, "Project X");       Larry.ProcessRequest(p);       p = new Purchase(2036, 122100.00, "Project Y");       Larry.ProcessRequest(p);        // Wait for user       Console.Read();     }   }    // "Handler"    abstract class Approver   {      protected Approver successor;      public void SetSuccessor(Approver successor)     {        this.successor = successor;     }      public abstract void ProcessRequest(Purchase purchase);   }    // "ConcreteHandler"    class Director : Approver   {      public override void ProcessRequest(Purchase purchase)     {        if (purchase.Amount < 10000.0)       {         Console.WriteLine("{0} approved request# {1}",            this.GetType().Name, purchase.Number);       }        else if (successor != null)       {         successor.ProcessRequest(purchase);       }     }   }    // "ConcreteHandler"    class VicePresident : Approver   {      public override void ProcessRequest(Purchase purchase)     {        if (purchase.Amount < 25000.0)       {         Console.WriteLine("{0} approved request# {1}",            this.GetType().Name, purchase.Number);       }        else if (successor != null)       {         successor.ProcessRequest(purchase);       }     }   }    // "ConcreteHandler"    class President : Approver   {      public override void ProcessRequest(Purchase purchase)     {        if (purchase.Amount < 100000.0)       {         Console.WriteLine("{0} approved request# {1}",            this.GetType().Name, purchase.Number);       }        else       {         Console.WriteLine(           "Request# {0} requires an executive meeting!",           purchase.Number);       }     }   }    // Request details    class Purchase   {      private int number;      private double amount;      private string purpose;      // Constructor      public Purchase( int number, double amount, string purpose)     {        this.number = number;        this.amount = amount;        this.purpose = purpose;     }      // Properties      public double Amount     {        get{ return amount; }        set{ amount = value; }     }      public string Purpose     {        get{ return purpose; }        set{ purpose = value; }     }      public int Number     {        get{ return number; }        set{ number = value; }     }   } }