下面是设计的UML类图：
类总括：
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6
7 namespace Club
8 {
9 class Program
10 {
11 static void Main(string[] args)
12 {
13 Account account = new Account("Legend", 270);
14 Console.WriteLine("Successed!");
15 Console.WriteLine("Name:{0}", account.Owner);
16 Console.WriteLine("Initial:{0}", account.Balance);
17 Console.WriteLine("------------------");
18
19 account.Cost(250);
20 Console.WriteLine("-----------------------------------------");
21
22 account.Deposit(100);
23 Console.WriteLine("-------------------");
24
25 account.Deposit(200);
26 Console.WriteLine("-----------------------------------------");
27
28 account.Cost(300);
29 Console.WriteLine("--------------------");
30
31 account.Deposit(999);
32 Console.WriteLine("-----------------------------------------");
33
34 account.Cost(700);
35 Console.WriteLine("---------------------");
36
37 account.Cost(123);
38 Console.WriteLine("-----------------------------------------");
39
40 Console.ReadLine();
41 }
42 }
43 }
44 class Account
45 {
46 public ClientState State{get;set;}
47 public string Owner{get;set;}
48 public double Balance{get;set;}
49
50 public Account(string owner,double initialAmount)
51 {
52 Owner=owner;
53 Balance=initialAmount;
54 State=new VistorState(this);
55 }
56
57 public void SetBalance(double amount)
58 {
59 Balance=amount;
60 }
61
62 public void Deposit(double amount)
63 {
64 Console.WriteLine("Now,deposit {0}.", amount);
65 State.Deposit(amount);
66 Console.WriteLine("ClientState turn to {0}", State);
67 }
68
69 public void Cost(double amount)
70 {
71 Console.WriteLine("Now,Cost {0}.", amount);
72 State.Cost(amount);
73 Console.WriteLine("ClientState turn to {0}", State);
74 }
75 }
76 abstract class ClientState
77 {
78 protected Account Account;
79 public abstract void Deposit(double amount);
80 public abstract void Cost(double amount);
81 public abstract void Check();
82 }
83 class VistorState : ClientState
84 {
85 public VistorState(Account account)
86 {
87 Account=account;
88 }
89
90 public override void Deposit(double amount)
91 {
92 Account.Balance+=amount;
93 Console.WriteLine("Deposit {0} to {1},surplus of account have {2} affter deposit", amount, Account.Owner, Account.Balance);
94 Check();
95 }
96
97 public override void Cost(double amount)
98 {
99 double newBalance=Account.Balance-amount;
100 Account.Balance-=amount;
101 Console.WriteLine("Cost {0} from {1},surplus of account have {2} affter cost", amount, Account.Owner, Account.Balance);
102 Check();
103 }
104 public override void Check()
105 {
106 if(Account.Balance>100 && Account.Balance<1000)
107 {
108 Account.State=new MemberState(Account);
109 }
110 else if(Account.Balance>=1000)
111 {
112 Account.State=new VIPState(Account);
113 }
114 }
115 }
116 class MemberState : ClientState
117 {
118 public MemberState(Account account)
119 {
120 Account=account;
121 }
122
123 public override void Deposit(double amount)
124 {
125 Account.Balance+=amount;
126 Console.WriteLine("Deposit {0} to {1},surplus of account have {2} affter deposit", amount, Account.Owner, Account.Balance);
127 Check();
128 }
129
130 public override void Cost(double amount)
131 {
132 double newBalance=Account.Balance-amount;
133 Account.Balance-=amount;
134 Console.WriteLine("Cost {0} from {1},surplus of account have {2} affter cost", amount, Account.Owner, Account.Balance);
135 Check();
136 }
137 public override void Check()
138 {
139 if(Account.Balance>0 && Account.Balance<=100)
140 {
141 Account.State = new VistorState(Account);
142 }
143 else if(Account.Balance>=1000)
144 {
145 Account.State=new VIPState(Account);
146 }
147 }
148 }
149 class VIPState : ClientState
150 {
151 public VIPState(Account account)
152 {
153 Account=account;
154 }
155
156 public override void Deposit(double amount)
157 {
158 Account.Balance+=amount;
159 Console.WriteLine("Deposit {0} to {1},surplus of account have {2} affter deposit", amount, Account.Owner, Account.Balance);
160 Check();
161 }
162
163 public override void Cost(double amount)
164 {
165 double newBalance=Account.Balance-amount;
166 Account.Balance-=amount;
167 Console.WriteLine("Cost {0} from {1},surplus of account have {2} affter cost", amount, Account.Owner, Account.Balance);
168 Check();
169 }
170 public override void Check()
171 {
172 if(Account.Balance>100 && Account.Balance<1000)
173 {
174 Account.State=new MemberState(Account);
175 }
176 else if (Account.Balance > 0 && Account.Balance <=100)
177 {
178 Account.State = new VistorState(Account);
179 }
180 }
181 }
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。