WCF学习笔记之消息交换模式

在WCF通信中，有三种消息交换模式，OneWay(单向模式), Request/Reponse(请求回复模式), Duplex(双工通信模式)这三种通信方式。下面对这三种消息交换模式进行讲解。

1. OneWay模式，

    [ServiceContract]
    public interface IOneWayService
    {
        [OperationContract(IsOneWay = true)]
        void Add(double x, double y);
    }

需要在OperationContract特性中显示的添加IsOneWay=true来标识这个操作是OneWay的，另外需要注意，此时的方法是不可以带返回值的。如果包含返回值，在启动Service后，可以看到下面截图所示的错误信息，

2. Request/Reponse模式，

当我们定义一个服务的操作时，该操作默认是请求回复模式的。不管该方法是否有返回值。可以通过Fiddler进行监控。

    [ServiceContract]
    public interface IRequestReponseService
    {
        [OperationContract]
        void Add(double x, double y);
    }

通过Fidder发现，当没有返回值时，其实服务给了一个默认的回复消息，

3. Duplex模式

定义双工通信：

    [ServiceContract(CallbackContract = typeof(IDuplexCallbackService))]
    public interface IDuplexService
    {
        [OperationContract(IsOneWay = true)]
        void GetDuplexServiceResult(string username, string password);
    }

    public interface IDuplexCallbackService
    {
        [OperationContract(IsOneWay = true)]
        void ShowDuplexServiceResult(IEnumerable<Department> depts);
    }

在定义服务契约时，同时指定回掉契约。

实现IDuplexService：

    public class DuplexService : IDuplexService
    {
        public void GetDuplexServiceResult(string username, string password)
        {
            if (string.IsNullOrWhiteSpace(username) ||
                string.IsNullOrWhiteSpace(password))
            {
                return;
            }

            if(username == "Yang-Fei" &&
                password == "")
            {
                List<Department> depts = new List<Department>()
                {
                    new Department() { Id = , Name="Development" },
                    new Department() { Id = , Name="Sales" },
                    new Department() { Id = , Name="Operation" },
                };

                IDuplexCallbackService callback =
                    OperationContext.Current.GetCallbackChannel<IDuplexCallbackService>();

                callback.ShowDuplexServiceResult(depts);
            }
        }
    }

我们可以使用netTcpBinding/wsDualHttpBinding来作为双工通信的binding。

App.config:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <startup>
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.2" />
    </startup>
  <system.serviceModel>
    <services>
      <service name="Services.DuplexService" behaviorConfiguration="DuplexServiceBehavior">
        <endpoint address="" binding="netTcpBinding" contract="Services.IDuplexService">
          <identity>
            <dns value="localhost"/>
          </identity>
        </endpoint>
        <endpoint address="mex" binding="netTcpBinding" contract="IMetadataExchange"/>
        <host>
          <baseAddresses>
            <add baseAddress="net.tcp://10.12.65.145/DuplexService"/>
          </baseAddresses>
        </host>
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior name="DuplexServiceBehavior">
          <serviceMetadata httpGetEnabled="false"/>
          <serviceDebug includeExceptionDetailInFaults="true"/>
        </behavior>
      </serviceBehaviors>
    </behaviors>
  </system.serviceModel>
</configuration>

需要在客户端实现回掉服务，例如：

    public class DuplexCallbackServiceClient : IDuplexServiceCallback
    {
        public void ShowDuplexServiceResult(Department[] depts)
        {
            foreach (Department dept in depts)
            {
                Console.WriteLine("Dept Id: {0} Dept Name: {1}", dept.Id, dept.Name);
            }
        }
    }

对服务进行调用：

        static void Main(string[] args)
        {
            DuplexCallbackServiceClient client = new DuplexCallbackServiceClient();

            InstanceContext context = new InstanceContext(client);

            using (DuplexServiceClient proxy = new DuplexServiceClient(context))
            {
                string username = "Yang-Fei";

                string password = "";

                proxy.GetDuplexServiceResult(username, password);
            }

            Console.ReadKey();
        }

运行结果：

代码点击这里下载，

感谢您的阅读。