基本上，把switch,用设计模式代替，肯定是bug和过度设计。想想，本来修改一个文件几行代码可以解决的问题，变成修改3-6个类才能实现一样的功能。不是傻是什么？...

那些迷信设计模式的人，来修改一下这个方法吧。看看你最终的代码膨胀为几倍。。。

 1   public virtual PasswordChangeResult ChangePassword(ChangePasswordRequest request)
 2     {
 3         if (request == null)
 4             throw new ArgumentNullException("request");
 5 
 6         var result = new PasswordChangeResult();
 7         if (String.IsNullOrWhiteSpace(request.Email))
 8         {
 9             result.AddError(_localizationService.GetResource("Account.ChangePassword.Errors.EmailIsNotProvided"));
10             return result;
11         }
12         if (String.IsNullOrWhiteSpace(request.NewPassword))
13         {
14             result.AddError(_localizationService.GetResource("Account.ChangePassword.Errors.PasswordIsNotProvided"));
15             return result;
16         }
17 
18         var customer = _customerService.GetCustomerByEmail(request.Email);
19         if (customer == null)
20         {
21             result.AddError(_localizationService.GetResource("Account.ChangePassword.Errors.EmailNotFound"));
22             return result;
23         }
24 
25 
26         var requestIsValid = false;
27         if (request.ValidateRequest)
28         {
29             //password
30             string oldPwd = "";
31             switch (customer.PasswordFormat)
32             {
33                 case PasswordFormat.Encrypted:
34                     oldPwd = _encryptionService.EncryptText(request.OldPassword);
35                     break;
36                 case PasswordFormat.Hashed:
37                     oldPwd = _encryptionService.CreatePasswordHash(request.OldPassword, customer.PasswordSalt, _customerSettings.HashedPasswordFormat);
38                     break;
39                 default:
40                     oldPwd = request.OldPassword;
41                     break;
42             }
43 
44             bool oldPasswordIsValid = oldPwd == customer.Password;
45             if (!oldPasswordIsValid)
46                 result.AddError(_localizationService.GetResource("Account.ChangePassword.Errors.OldPasswordDoesntMatch"));
47 
48             if (oldPasswordIsValid)
49                 requestIsValid = true;
50         }
51         else
52             requestIsValid = true;
53 
54 
55         //at this point request is valid
56         if (requestIsValid)
57         {
58             switch (request.NewPasswordFormat)
59             {
60                 case PasswordFormat.Clear:
61                     {
62                         customer.Password = request.NewPassword;
63                     }
64                     break;
65                 case PasswordFormat.Encrypted:
66                     {
67                         customer.Password = _encryptionService.EncryptText(request.NewPassword);
68                     }
69                     break;
70                 case PasswordFormat.Hashed:
71                     {
72                         string saltKey = _encryptionService.CreateSaltKey(5);
73                         customer.PasswordSalt = saltKey;
74                         customer.Password = _encryptionService.CreatePasswordHash(request.NewPassword, saltKey, _customerSettings.HashedPasswordFormat);
75                     }
76                     break;
77                 default:
78                     break;
79             }
80             customer.PasswordFormat = request.NewPasswordFormat;
81             _customerService.UpdateCustomer(customer);
82         }
83 
84         return result;
85     }