Give an example of a duplex service

[ServiceContract(SessionMode=SessionMode.Required,

                 CallbackContract=typeof(IRespondBackCallback))]

public interface ICalculatorDuplex

{

    [OperationContract(IsOneWay = true)]

    void FunctionClientCanCall();

}



public interface IRespondBackCallback

{

    [OperationContract(IsOneWay = true)]

    void FunctionServiceCanCall(double result);

}