Question

//WCF Services Code:
    [ServiceContract(Namespace = "Silverlight", CallbackContract = typeof(IStockServiceClient))]
    public interface IStockService
    {
        [OperationContract(IsOneWay = false)]
        void Connect();
    }

    [ServiceContract]
    public interface IStockServiceClient
    {
        [OperationContract(IsOneWay = true)]
        int SendUpdate(string value);
    }

    public class StockService : IStockService
    {
        private static IStockServiceClient client;
        public void Connect()
        {
            client = OperationContext.Current.GetCallbackChannel<IStockServiceClient>();
        }
        public static IStockServiceClient Client
        {
            get
            {
                return client;
            }
        }
    }

//Call Silverlight Code
    private void button1_Click(object sender, RoutedEventArgs e)
    {
       var result = DuplexStockService.Web.StockService.Client.
                SendUpdate("test");
    }


//silverlight code
   private void button1_Click(object sender, RoutedEventArgs e)
   {
            ServiceReference1.StockServiceClient client =
                new ServiceReference1.StockServiceClient();
            client.ConnectAsync();
            client.SendUpdateReceived += (senderSendUpdateReceived, eSendUpdateReceived) =>
                {
                    //return 1; //Doesn't work
                    //How to return a value back to WCF?
                };
   }

回调方法int SendUpdate（字符串值）应该返回一个int值，但是silverlight的SendUpdateReceived事件处理程序如何将一个int值返回给它的wcf被调用者？

Answer 1

如果您的操作合同标记为OneWay，则无法返回任何值。所有单向操作必须返回void，因为客户端永远不会等待他们的响应 - 这就是为什么它们被单向调用的原因。

Answer 2

Silverlight不支持您所要求的内容 - 回调只能是不返回值的单向操作。这是Silverlight对双工服务的额外限制 - 在非Silverlight WCF中，您可以指定所需的任何返回类型。

与net.tcp的双工通信：如何从CallbackContract获取返回值

2 个答案: