多项选择题 You are developing a Windows Communication Foundation (WCF) service that returns location information for authorized law enforcement agencies. The service contract is as follows: [ServiceContract] public interface IMappingService { [OperationContract] long[] GetLocationCoordinates(String cityName); [OperationContract] long[] GetLocationOfCitizen(String ssn); } Users are authenticated and impersonated. The system uses ASP.NET roles. The members of law enforcement are members of the LawEnforcement role. You need to ensure that only members of the LawEnforcement role can call these methods. What are two possible ways to achieve this goal?（） (Each correct answer presents a complete solution. Choose two.)

单项选择题 You need to modify a client application that consumes a Windows Communication Foundation (WCF) service. The service metadata is no longer available. You need to modify the previously generated proxy to include asynchronous calls to the service. What should you do? （）

单项选择题 following code segment. [ServiceContract] public interface ICustomerService { ... } public class CustomerService : ICustomerService { ... } The service is self-hosted in a console application. Older client applications access the service at http://contoso.com:8080/CustomerService/V1. Newer client applications access the service at http://contoso.com:8080/CustomerService/V2. You need to ensure that any client application can access the service at either address. Which code segment should you use?（）