How to to access the response value with in the WCF callback handler while communicating with the WCF service hosted as server from client side in ASP.NET with C#?

[ServiceContract(CallbackContract = typeof(IServiceCallback))]
    public interface IService1
    {
        [OperationContract(IsOneWay = true)]
        Task Hello(string messsage);
    }

    public interface IServiceCallback
    {
        [OperationContract(IsOneWay = true)]
        Task OnHello(string message);
    }

<pre>  Task IService1.Hello(string messsage)
        {
            var callback = OperationContext.Current.GetCallbackChannel<IServiceCallback>();
            return callback.OnHello("You Said:" + messsage);


        }

protected void btnGetResponse_Click(object sender, EventArgs e)
        {
            var context = new InstanceContext(new WCFServiceCallbackHandler());
            var client = new ServiceReference1.Service1Client(context);

           

            bool exit = false;
            Console.WriteLine("Enter X to exit:");
            Console.WriteLine("Write and enter to send something to server:");

           
            while (!exit)
            {
                Console.WriteLine("Client:");

                String stringToSend = txtMsgToServer.Text;
                if (stringToSend.ToUpper() != "X")
                {
                    client.Hello(stringToSend);
                }
                else { exit = true; }
               
            }

            
           

          
        }
          
    }

    public class WCFServiceCallbackHandler : ServiceReference1.IService1Callback
    {
        public string result { get; set; }

        void ServiceReference1.IService1Callback.OnHello(string message)
        {
            Console.WriteLine(message);
                    result = message;
             
            //HttpContext context = HttpContext.Current;
            //context.Session["message"] = message;

        }