You are creating a workflow application by using Microsoft .NET Framework 3.5. The application uses local communication. The workflow host must receive data from an existing workflow instance. You need to define the communication between the workflow host and the workflow instance. Which code segment should you use?
A.
[ExternalDataExchange]public interface ICommunicationService { void CallHost(string someData);}
B.
[ExternalDataExchange]public interface ICommunicationService { event
EventHandler<ExternalDataEventArgs> CallHost;}
C.
public class CommunicationService : ExternalDataExchangeService { public event EventHandler<ExternalDataEventArgs> CallHost;}
D.
public class CommunicationService : ExternalDataExchangeService { public void CallHost(string someData) { base.AddService(this); }}