State

// State pattern -- Real World example

using System; namespace DoFactory.GangOfFour.State.RealWorld {       // MainApp test application    class MainApp   {      static void Main()     {        // Open a new account       Account account = new Account("Jim Johnson");        // Apply financial transactions       account.Deposit(500.0);       account.Deposit(300.0);       account.Deposit(550.0);       account.PayInterest();       account.Withdraw(2000.00);       account.Withdraw(1100.00);        // Wait for user       Console.Read();     }   }    // "State"    abstract class State   {      protected Account account;      protected double balance;      protected double interest;      protected double lowerLimit;      protected double upperLimit;      // Properties      public Account Account     {        get{ return account; }        set{ account = value; }     }      public double Balance     {        get{ return balance; }        set{ balance = value; }     }      public abstract void Deposit( double amount);      public abstract void Withdraw( double amount);      public abstract void PayInterest();   }    // "ConcreteState"    // Account is overdrawn    class RedState : State   {      double serviceFee;      // Constructor      public RedState(State state)     {        this.balance = state.Balance;        this.account = state.Account;       Initialize();     }      private void Initialize()     {        // Should come from a datasource       interest = 0.0;       lowerLimit = -100.0;       upperLimit = 0.0;       serviceFee = 15.00;     }      public override void Deposit( double amount)     {       balance += amount;       StateChangeCheck();     }      public override void Withdraw( double amount)     {       amount = amount - serviceFee;       Console.WriteLine("No funds available for withdrawal!");     }      public override void PayInterest()     {        // No interest is paid     }      private void StateChangeCheck()     {        if (balance > upperLimit)       {         account.State = new SilverState( this);       }     }   }    // "ConcreteState"    // Silver is non-interest bearing state    class SilverState : State   {      // Overloaded constructors      public SilverState(State state) :        this( state.Balance, state.Account)     {       }      public SilverState( double balance, Account account)     {        this.balance = balance;        this.account = account;       Initialize();     }      private void Initialize()     {        // Should come from a datasource       interest = 0.0;       lowerLimit = 0.0;       upperLimit = 1000.0;     }      public override void Deposit( double amount)     {       balance += amount;       StateChangeCheck();     }      public override void Withdraw( double amount)     {       balance -= amount;       StateChangeCheck();     }      public override void PayInterest()     {       balance += interest * balance;       StateChangeCheck();     }      private void StateChangeCheck()     {        if (balance < lowerLimit)       {         account.State = new RedState( this);       }        else if (balance > upperLimit)       {         account.State = new GoldState( this);       }     }   }    // "ConcreteState"    // Interest bearing state    class GoldState : State   {      // Overloaded constructors      public GoldState(State state)       : this(state.Balance,state.Account)     {       }      public GoldState( double balance, Account account)     {        this.balance = balance;        this.account = account;       Initialize();     }      private void Initialize()     {        // Should come from a database       interest = 0.05;       lowerLimit = 1000.0;       upperLimit = 10000000.0;     }      public override void Deposit( double amount)     {       balance += amount;       StateChangeCheck();     }      public override void Withdraw( double amount)     {       balance -= amount;       StateChangeCheck();     }      public override void PayInterest()     {       balance += interest * balance;       StateChangeCheck();     }      private void StateChangeCheck()     {        if (balance < 0.0)       {         account.State = new RedState( this);       }        else if (balance < lowerLimit)       {         account.State = new SilverState( this);       }     }   }    // "Context"    class Account   {      private State state;      private string owner;      // Constructor      public Account( string owner)     {        // New accounts are 'Silver' by default        this.owner = owner;       state = new SilverState(0.0, this);     }      // Properties      public double Balance     {        get{ return state.Balance; }     }      public State State     {        get{ return state; }        set{ state = value; }     }      public void Deposit( double amount)     {       state.Deposit(amount);       Console.WriteLine("Deposited {0:C} --- ", amount);       Console.WriteLine(" Balance = {0:C}", this.Balance);       Console.WriteLine(" Status = {0}\n" ,          this.State.GetType().Name);       Console.WriteLine("");     }      public void Withdraw( double amount)     {       state.Withdraw(amount);       Console.WriteLine("Withdrew {0:C} --- ", amount);       Console.WriteLine(" Balance = {0:C}", this.Balance);       Console.WriteLine(" Status = {0}\n" ,          this.State.GetType().Name);     }      public void PayInterest()     {       state.PayInterest();       Console.WriteLine("Interest Paid --- ");       Console.WriteLine(" Balance = {0:C}", this.Balance);       Console.WriteLine(" Status = {0}\n" ,          this.State.GetType().Name);     }   } }