A Windows Communication Foundation (WCF) solution uses the following contracts. (Line numbers are included for reference only.)<br /> 01 [ServiceContract(CallbackContract=typeof(INameService))]<br /> 02 public interface IGreetingService<br /> 03 {<br /> 04 [OperationContract]<br /> 05 string GetMessage();<br /> 06 }<br /> 07 [ServiceContract]<br /> 08 public interface INameService<br /> 09 {<br /> 10 [OperationContract]<br /> 11 string GetName();<br /> 12 }<br /> The code that implements the IGreetingService interface is as follows:<br /> 20 public class GreetingService : IGreetingService<br /> 21{<br /> 22 public string GetMessage()<br /> 23 {<br /> 24 INameService clientChannel = OperationContext.Current.GetCallbackChannel<inameservice>();<br /> 25 string clientName = clientChannel.GetName();<br /> 26 return String.Format(&quot;Hello {0}&quot;, clientName);<br /> 27 }<br /> 28 }<br /> The service is self-hosted. The hosting code is as follows:<br /> 30 ServiceHost host = new ServiceH