单项选择题 A Windows Communication Foundation (WCF) service is hosted in Microsoft Internet Information Services (IIS). You are preparing the configuration file for production deployment. You need to set up tracing so that an administrator can adjust the System.ServiceModel trace level without causing the ASP.NET host application domain to restart. You need to ensure that tracing is turned off by default. What should you do?（）

单项选择题 You are developing a Windows Communication Foundation (WCF) service to replace an existing ASMX Web service.The WCF service contains the following code segment. (Line numbers are included for reference only.) 01 [ServiceContract()] 02 03 public interface IEmployeeService 04 { 05 [OperationContract()] 06 EmployeeInfo GetEmployeeInfo(int employeeID); 07 08 } 09 10 public class EmployeeService : IEmployeeService 11 { 12 13 public EmployeeInfo GetEmployeeInfo(int employeeID) 14 { 15 ... 16 } 17 } 18 19 20 public class EmployeeInfo 21 { 22 ... 23 public int EmployeeID { get; set; } 24 public string FirstName { get; set; } 25 public string LastName { get; set; } 26 27 }The existing Web service returns the EmployeelD as an attribute of the Employeelnfo element in the response XML.You need to ensure that applications can consume the service without code changes in the client. What should you do?（）

单项选择题 You are developing a Windows Communication Foundation (WCF) service that contains the following service contract.[ServiceContract()]public interface IPaymentService{ [OperationContract()] void RecordPayments(Person person);}public class Person{ ... }public class Employee : Person{ ... }public class Customer : Person{ ... }You need to ensure that RecordPayments can correctly deserialize into an Employee or a Customer object. What should you do?（）