状态者模式

下面是设计的UML类图：

类总括：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Club
{
    class Program
    {
        static void Main(string[] args)
        {
            Account account = new Account("Legend", 270);
            Console.WriteLine("Successed!");
            Console.WriteLine("Name:{0}", account.Owner);
            Console.WriteLine("Initial:{0}", account.Balance);
            Console.WriteLine("------------------");

            account.Cost(250);
            Console.WriteLine("-----------------------------------------");

            account.Deposit(100);
            Console.WriteLine("-------------------");

            account.Deposit(200);
            Console.WriteLine("-----------------------------------------");

            account.Cost(300);
            Console.WriteLine("--------------------");

            account.Deposit(999);
            Console.WriteLine("-----------------------------------------");

            account.Cost(700);
            Console.WriteLine("---------------------");

            account.Cost(123);
            Console.WriteLine("-----------------------------------------");

            Console.ReadLine();
        }
    }
}
class Account
{
    public ClientState State{get;set;}
    public string Owner{get;set;}
    public double Balance{get;set;}

    public Account(string owner,double initialAmount)
    {
        Owner=owner;
        Balance=initialAmount;
        State=new VistorState(this);
    }

    public void SetBalance(double amount)
    {
        Balance=amount;
    }

    public void Deposit(double amount)
    {
        Console.WriteLine("Now,deposit {0}.", amount);
        State.Deposit(amount);
        Console.WriteLine("ClientState turn to {0}", State);
    }

    public void Cost(double amount)
    {
        Console.WriteLine("Now,Cost {0}.", amount);
        State.Cost(amount);
        Console.WriteLine("ClientState turn to {0}", State);
    }
}
abstract class ClientState
{
    protected Account Account;
    public abstract void Deposit(double amount);
    public abstract void Cost(double amount);
    public abstract void Check();
}
class VistorState : ClientState
{
    public VistorState(Account account)
    {
        Account=account;
    }

    public override void Deposit(double amount)
    {
         Account.Balance+=amount;
        Console.WriteLine("Deposit {0} to {1},surplus of account have {2} affter deposit", amount, Account.Owner, Account.Balance);
        Check();
    }

    public override void Cost(double amount)
    {
         double newBalance=Account.Balance-amount;
        Account.Balance-=amount;
        Console.WriteLine("Cost {0} from {1},surplus of account have {2} affter cost", amount, Account.Owner, Account.Balance);
        Check();
    }
    public override void Check()
    {
         if(Account.Balance>100 && Account.Balance<1000)
        {
            Account.State=new MemberState(Account);
        }
        else if(Account.Balance>=1000)
        {
             Account.State=new VIPState(Account);
        }
    }
}
class MemberState : ClientState
{
    public MemberState(Account account)
    {
        Account=account;
    }

    public override void Deposit(double amount)
    {
         Account.Balance+=amount;
        Console.WriteLine("Deposit {0} to {1},surplus of account have {2} affter deposit", amount, Account.Owner, Account.Balance);
        Check();
    }

    public override void Cost(double amount)
    {
         double newBalance=Account.Balance-amount;
        Account.Balance-=amount;
        Console.WriteLine("Cost {0} from {1},surplus of account have {2} affter cost", amount, Account.Owner, Account.Balance);
        Check();
    }
    public override void Check()
    {
         if(Account.Balance>0 && Account.Balance<=100)
        {
            Account.State = new VistorState(Account);
        }
        else if(Account.Balance>=1000)
        {
             Account.State=new VIPState(Account);
        }
    }
}
class VIPState : ClientState
{
    public VIPState(Account account)
    {
        Account=account;
    }

    public override void Deposit(double amount)
    {
         Account.Balance+=amount;
        Console.WriteLine("Deposit {0} to {1},surplus of account have {2} affter deposit", amount, Account.Owner, Account.Balance);
        Check();
    }

    public override void Cost(double amount)
    {
         double newBalance=Account.Balance-amount;
        Account.Balance-=amount;
        Console.WriteLine("Cost {0} from {1},surplus of account have {2} affter cost", amount, Account.Owner, Account.Balance);
        Check();
    }
    public override void Check()
    {
         if(Account.Balance>100 && Account.Balance<1000)
        {
            Account.State=new MemberState(Account);
        }
        else if (Account.Balance > 0 && Account.Balance <=100)
        {
            Account.State = new VistorState(Account);
        }
    }
}

运行结果：

优点：

　　1.封装了转换规则；

　　2. 方便增加 新的状态；

　　3. 允许状态转换逻辑与状态对象合成一体；

　　4. 环境对象可共享状态对象。

缺点：

　　1.结构及实现复杂；

　　2.代码更显得累赘；

　　3.不太支持OCP。