1 public class User
2 {
3     　　public void ChangeUsername(string newUsername)
4     　　{
5             　　//使用服务定位器获取IUsernameUniqueService ，执行验证。
6     　　}
7 }

 1 public class User
 2 {
 3         public void ChangeUsername(string newUsername)
 4         {
 5         　　　　EventBus.Send(new  UsernameChangedEvent(newUsername));
 6         }
 7 }
 8
 9 public class UsernameChangedEventHandler
10 {
11         public UsernameChangedEventHandler(IUsernameUniqueService usernameUniqueService){}
12
13         public void Process(UsernameChangedEvent){}
14 }

 1 public class ChangeUsernameCommandHandler
 2 {
 3         public ChangeUsernameCommandHandler(IUsernameUniqueService usernameUniqueService){}
 4
 5         public void Process(ChageUsernameCommand){}
 6 }
 7
 8 public class User
 9 {
10         public void ChangeUsername(IUsernameUniqueService usernameUniqueService, newUsername){}
11 }

 1 public class UsernameChangeService
 2 {
 3     　　public UsernameChangeService(IUsernameUniqueService usernameUniqueService){}
 4
 5     　　public void ChangeUsername(Guid userId, string newUsername){ }
 6 }
 7
 8 public class User
 9 {
10     　　Internal void ChangeUsername(string newUsername){ }
11 }

 1 public class UsingUser
 2 {
 3     　　public UsingUser(User user, IUsernameUniqueService usernameUniqueService){}
 4
 5     　　public void ChangeUsername(string newUsername){ }
 6 }
 7
 8 public class User
 9 {
10     　　Internal void ChangeUsername(string newUsername){  }
11 }