A Windows Communication Foundation (WCF) solution uses the following contracts. (Line numbers are included for reference only.) 01 [ServiceContract(CallbackContract=typeof(INameService))] 02 public interface IGreetingService 03 { 04 [OperationContract] 05 string GetMessage（ ）; 06 } 07 [ServiceContract] 08 public interface INameService 09 { 10 [OperationContract] 11 string GetName（ ）; 12 } The code that implements the IGreetingService interface is as follows: 20 public class GreetingService : IGreetingService 21{ 22 public string GetMessage（ ） 23 { 24 INameService clientChannel = OperationContext.Current.GetCallbackChannel（ ）; 25 string clientName = clientChannel.GetName（ ）; 26 return String.Format("Hello {0}", clientName); 27 } 28 } The service is self-hosted. The hosting code is as follows: 30 ServiceHost host = new ServiceHost(typeof(GreetingService)); 31 NetTcpBinding binding = new NetTcpBinding(SecurityMode.None); 32 host.AddServiceEndpoint("MyApplication.IGreetingService", binding, "net.tcp//localhost:12345"); 33 host.Open（ ）; The code that implements the lNameService interface is as follows: 40 class NameService : INameService 41 { 42 string name; 43 public NameService(string name) 44 { 45 this.name = name; 46 } 47 public string GetName（ ） 48 { 49 return name; 50 } 51 } Currently, this code fails at runtime, and an InvalidOperationException is thrown at line 25. You need to correct the code so that the call from the service back to the client completes successfully. What are two possible ways to achieve this goal? (Each correct answer presents a complete solution. Choose two.)（）
正确答案:C,D
答案解析:有
