2.0通信之调用WCF的双向通信(Duplex Service)

介绍
Silverlight 2.0 调用 WCF 的双向通信服务(Duplex Service) 。开发一个服务端主动向客服端发送股票信息的程序，首先客户端先向服务端发送需要监控的股票的股票代码，然后服务端在该股信息发生变化的时候将信息推送到客户端。
    服务端：
        定义服务契约及回调接口
        从当前上下文获取回调的客户端信道
        需要的话则向客户端信道“推”消息
    客户端：
        构造 PollingDuplexHttpBinding 并在其上创建 IDuplexSessionChannel 的信道工厂
        异步方式打开信道工厂
        异步方式打开信道
        构造需要发送到服务端的消息 System.ServiceModel.Channels.Message
        异步向服务端发送消息
        监听指定信道，用于异步方式接收服务端返回的消息
        不需要再接收服务端的消息则关闭信道


在线DEMO
http://www.cnblogs.com/webabcd/archive/2008/10/09/1307486.html


示例
服务端：
IDuplexService.cs

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Runtime.Serialization;
using  System.ServiceModel;
using  System.Text;

using  System.ServiceModel.Channels;

/**/ /// <summary>
/// IDuplexService - 双工（Duplex）服务契约
/// CallbackContract - 双工（Duplex）服务的回调类型
/// </summary>
[ServiceContract(Namespace  =   " Silverlight20 " , CallbackContract  =   typeof (IDuplexClient))]
public   interface  IDuplexService
{
    /**//// <summary>
    /// 客户端向服务端发送消息的方法
    /// </summary>
    /// <param name="receivedMessage">客户端向服务端发送的消息 System.ServiceModel.Channels.Message</param>
    [OperationContract(IsOneWay = true)]
    void SendStockCode(Message receivedMessage);
}

/**/ /// <summary>
/// 双工（Duplex）服务的回调接口
/// </summary>
public   interface  IDuplexClient
{
    /**//// <summary>
    /// 客户端接收服务端发送过来的消息的方法
    /// </summary>
    /// <param name="returnMessage">服务端向客户端发送的消息 System.ServiceModel.Channels.Message</param>
    [OperationContract(IsOneWay = true)]
    void ReceiveStockMessage(Message returnMessage);
}

DuplexService.cs

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Runtime.Serialization;
using  System.ServiceModel;
using  System.Text;

using  System.ServiceModel.Channels;
using  System.Threading;
using  System.ServiceModel.Activation;
using  System.IO;

/**/ /// <summary>
/// Duplex 服务的服务端的实现
/// 本文以客户端向服务端提交股票代码，服务端定时向客户端发送股票信息为例
/// </summary>
public   class  DuplexService : IDuplexService
{
    IDuplexClient _client;
    bool _status = true;

    /**//// <summary>
    /// 客户端向服务端发送股票代码的方法
    /// </summary>
    /// <param name="receivedMessage">包含股票代码的 System.ServiceModel.Channels.Message </param>
    public void SendStockCode(Message receivedMessage)
    {
        // 获取当前上下文的回调信道
        _client = OperationContext.Current.GetCallbackChannel<IDuplexClient>();

        // 如果发生错误则不再执行
        OperationContext.Current.Channel.Faulted += new EventHandler(delegate { _status = false; });

        // 获取用户提交的股票代码
        string stockCode = receivedMessage.GetBody<string>();

        // 每3秒向客户端发送一次股票信息
        while (_status)
        {
            // 构造需要发送到客户端的 System.ServiceModel.Channels.Message
            // Duplex 服务仅支持 Soap11 ， Action 为请求的目的地（需要执行的某行为的路径）
            Message stockMessage = Message.CreateMessage(
                MessageVersion.Soap11,
                "Silverlight20/IDuplexService/ReceiveStockMessage",
                string.Format("StockCode: {0}; StockPrice: {1}; CurrentTime: {2}",
                    stockCode,
                    new Random().Next(1, 200),
                    DateTime.Now.ToString()));

            try
            {
                // 向客户端“推”数据
                _client.ReceiveStockMessage(stockMessage);
            }
            catch (Exception ex)
            {
                // 出错则记日志
                using (StreamWriter sw = new StreamWriter(@"C:\Silverlight_Duplex_Log.txt", true))
                {
                    sw.Write(ex.ToString());
                    sw.WriteLine();
                }
            }

            System.Threading.Thread.Sleep(3000);
        }
    }
}

PollingDuplexServiceHostFactory.cs

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Web;

using  System.ServiceModel;
using  System.ServiceModel.Channels;
using  System.ServiceModel.Activation;

/**/ /* 以下部分摘自文档 */

//  服务 svc 文件的 Factory 要指定为此类
public   class  PollingDuplexServiceHostFactory : ServiceHostFactoryBase
{
    public override ServiceHostBase CreateServiceHost(string constructorString,
        Uri[] baseAddresses)
    {
        return new PollingDuplexSimplexServiceHost(baseAddresses);
    }
}

class  PollingDuplexSimplexServiceHost : ServiceHost
{
    public PollingDuplexSimplexServiceHost(params System.Uri[] addresses)
    {
        base.InitializeDescription(typeof(DuplexService), new UriSchemeKeyedCollection(addresses));
    }

    protected override void InitializeRuntime()
    {
        // 配置 WCF 服务与 Silverlight 客户端之间的 Duplex 通信
        // Silverlight 客户端定期轮询网络层上的服务，并检查回调信道上由服务端发送的所有新的消息
        // 该服务会将回调信道上的由服务端发送的所有消息进行排队，并在客户端轮询服务时将这些消息传递到该客户端

        PollingDuplexBindingElement pdbe = new PollingDuplexBindingElement()
        {
            // ServerPollTimeout - 轮询超时时间
            // InactivityTimeout - 服务端与客户端在此超时时间内无任何消息交换的情况下，服务会关闭其会话

            ServerPollTimeout = TimeSpan.FromSeconds(3),
            InactivityTimeout = TimeSpan.FromMinutes(1)
        };

        // 为服务契约（service contract）添加一个终结点（endpoint）
        // Duplex 服务仅支持 Soap11
        this.AddServiceEndpoint(
            typeof(IDuplexService),
            new CustomBinding(
                pdbe,
                new TextMessageEncodingBindingElement(
                    MessageVersion.Soap11,
                    System.Text.Encoding.UTF8),
                new HttpTransportBindingElement()),
                "");

        base.InitializeRuntime();
    }
}

DuplexService.svc

<% @ ServiceHost Language="C#" Debug="true" Service="DuplexService" CodeBehind="~/App_Code/DuplexService.cs" Factory="PollingDuplexServiceHostFactory"  %>

客户端：
DuplexService.xaml

< UserControl  x:Class ="Silverlight20.Communication.DuplexService"
    xmlns ="http://schemas.microsoft.com/winfx/2006/xaml/presentation"  
    xmlns:x ="http://schemas.microsoft.com/winfx/2006/xaml" >
     < StackPanel  HorizontalAlignment ="Left"  Margin ="5" >
    
         < TextBox  x:Name ="txtStockCode"  Text ="请输入股票代码"  Margin ="5"   />
         < Button  x:Name ="btnSubmit"  Content ="获取股票信息"  Click ="btnSubmit_Click"  Margin ="5"   />
         < Button  x:Name ="btnStop"  Content ="停止获取"  Click ="btnStop_Click"   Margin ="5"   />
         < TextBlock  x:Name ="lblStockMessage"  Margin ="5"   />
    
     </ StackPanel >
</ UserControl >

DuplexService.xaml.cs

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Net;
using  System.Windows;
using  System.Windows.Controls;
using  System.Windows.Documents;
using  System.Windows.Input;
using  System.Windows.Media;
using  System.Windows.Media.Animation;
using  System.Windows.Shapes;

using  System.ServiceModel;
using  System.ServiceModel.Channels;
using  System.Threading;
using  System.IO;

namespace  Silverlight20.Communication
{
    public partial class DuplexService : UserControl
    {
        SynchronizationContext _syncContext;

        // 是否接收服务端发送过来的消息
        bool _status = true;

        public DuplexService()
        {
            InitializeComponent();
        }

        private void btnSubmit_Click(object sender, RoutedEventArgs e)
        {
            _status = true;

            // UI 线程
            _syncContext = SynchronizationContext.Current;

            PollingDuplexHttpBinding binding = new PollingDuplexHttpBinding()
            {
                // InactivityTimeout - 服务端与客户端在此超时时间内无任何消息交换的情况下，服务会关闭其会话
                InactivityTimeout = TimeSpan.FromMinutes(1)
            };

            // 构造 IDuplexSessionChannel 的信道工厂
            IChannelFactory<IDuplexSessionChannel> factory =
                binding.BuildChannelFactory<IDuplexSessionChannel>(new BindingParameterCollection());

            // 打开信道工厂
            IAsyncResult factoryOpenResult =
                factory.BeginOpen(new AsyncCallback(OnOpenCompleteFactory), factory);

            if (factoryOpenResult.CompletedSynchronously)
            {
                // 如果信道工厂被打开的这个 异步操作 已经被 同步完成 则执行下一步
                CompleteOpenFactory(factoryOpenResult);
            }
        }

        private void btnStop_Click(object sender, RoutedEventArgs e)
        {
            _status = false;
        }

        void OnOpenCompleteFactory(IAsyncResult result)
        {
            // 该异步操作已被同步完成的话则不做任何操作，反之则执行下一步
            if (result.CompletedSynchronously)
                return;
            else
                CompleteOpenFactory(result);
        }

        void CompleteOpenFactory(IAsyncResult result)
        {
            IChannelFactory<IDuplexSessionChannel> factory = result.AsyncState as IChannelFactory<IDuplexSessionChannel>;

            // 完成异步操作，以打开信道工厂
            factory.EndOpen(result);

            // 在信道工厂上根据指定的地址创建信道
            IDuplexSessionChannel channel =
                factory.CreateChannel(new EndpointAddress("http://localhost:3036/DuplexService.svc"));

            // 打开信道
            IAsyncResult channelOpenResult =
                channel.BeginOpen(new AsyncCallback(OnOpenCompleteChannel), channel);

            if (channelOpenResult.CompletedSynchronously)
            {
                // 如果信道被打开的这个 异步操作 已经被 同步完成 则执行下一步
                CompleteOpenChannel(channelOpenResult);
            }
        }

        void OnOpenCompleteChannel(IAsyncResult result)
        {
            // 该异步操作已被同步完成的话则不做任何操作，反之则执行下一步
            if (result.CompletedSynchronously)
                return;
            else
                CompleteOpenChannel(result);
        }

        void CompleteOpenChannel(IAsyncResult result)
        {
            IDuplexSessionChannel channel = result.AsyncState as IDuplexSessionChannel;

            // 完成异步操作，以打开信道
            channel.EndOpen(result);

            // 构造需要发送到服务端的 System.ServiceModel.Channels.Message （客户端终结点与服务端终结点之间的通信单元）
            Message message = Message.CreateMessage(
                channel.GetProperty<MessageVersion>(), // MessageVersion.Soap11 （Duplex 服务仅支持 Soap11）
                "Silverlight20/IDuplexService/SendStockCode", // Action 为请求的目的地（需要执行的某行为的路径）
                txtStockCode.Text);

            // 向目的地发送消息
            IAsyncResult resultChannel =
                channel.BeginSend(message, new AsyncCallback(OnSend), channel);

            if (resultChannel.CompletedSynchronously)
            {
                // 如果向目的地发送消息的这个 异步操作 已经被 同步完成 则执行下一步
                CompleteOnSend(resultChannel);
            }

            // 监听指定的信道，用于接收返回的消息
            ReceiveLoop(channel);
        }

        void OnSend(IAsyncResult result)
        {
            // 该异步操作已被同步完成的话则不做任何操作，反之则执行下一步
            if (result.CompletedSynchronously)
                return;
            else
                CompleteOnSend(result);
        }

        void CompleteOnSend(IAsyncResult result)
        {
            try
            {
                IDuplexSessionChannel channel = (IDuplexSessionChannel)result.AsyncState;

                // 完成异步操作，以完成向目的地发送消息的操作
                channel.EndSend(result);
            }
            catch (Exception ex)
            {
                _syncContext.Post(WriteText, ex.ToString() + Environment.NewLine);
            }
        }

        void ReceiveLoop(IDuplexSessionChannel channel)
        {
            // 监听指定的信道，用于接收返回的消息
            IAsyncResult result = 
                channel.BeginReceive(new AsyncCallback(OnReceiveComplete), channel);

            if (result.CompletedSynchronously)
            {
                CompleteReceive(result);
            }
        }

        void OnReceiveComplete(IAsyncResult result)
        {
            if (result.CompletedSynchronously)
                return;
            else
                CompleteReceive(result);
        }

        void CompleteReceive(IAsyncResult result)
        {
            IDuplexSessionChannel channel = (IDuplexSessionChannel)result.AsyncState;

            try
            {
                // 完成异步操作，以接收到服务端发过来的消息
                Message receivedMessage = channel.EndReceive(result);

                if (receivedMessage == null)
                {
                    // 服务端会话已被关闭
                    // 此时应该关闭客户端会话，或向服务端发送消息以启动一个新的会话
                }
                else
                {
                    // 将接收到的信息输出到界面上
                    string text = receivedMessage.GetBody<string>();
                    _syncContext.Post(WriteText, text + Environment.NewLine);

                    if (!_status)
                    {
                        // 关闭信道
                        IAsyncResult resultFactory =
                            channel.BeginClose(new AsyncCallback(OnCloseChannel), channel);

                        if (resultFactory.CompletedSynchronously)
                        {
                            CompleteCloseChannel(result);
                        }

                    }
                    else
                    {
                        // 继续监听指定的信道，用于接收返回的消息
                        ReceiveLoop(channel);
                    }
                }
            }
            catch (Exception ex)
            {
                // 出错则记日志
                using (StreamWriter sw = new StreamWriter(@"C:\Silverlight_Duplex_Log.txt", true))
                {
                    sw.Write(ex.ToString());
                    sw.WriteLine();
                }
            }
        }

        void OnCloseChannel(IAsyncResult result)
        {
            if (result.CompletedSynchronously)
                return;
            else
                CompleteCloseChannel(result);
        }

        void CompleteCloseChannel(IAsyncResult result)
        {
            IDuplexSessionChannel channel = (IDuplexSessionChannel)result.AsyncState;

            // 完成异步操作，以关闭信道
            channel.EndClose(result);
        }

        void WriteText(object text)
        {
            // 将信息打到界面上
            lblStockMessage.Text += (string)text;
        }
    }
}