Silverlight与WCF之间的通信(2)利用WCF的双工通信“推送”给SL数据

一，Duplex简介

上一个随笔记录了SL利用Timer定时去WCF上取数据再绑定到界面上的问题，今天尝试用了WCF的Duplex双工通信来做这个事情，也以这个例子来说明WCF中Duplex的使用。

双工通信的原理很简单，我们平时用的是客户端调用服务端的方法来获取数据，而Duplex是将客户端也当作了服务器，客户端上的方法也可以被调用，以聊天功能为例子，用户A连接到服务器后，之前的做法是客户端定时取数据，而Duplex是在服务端定时检测数据变化，如果发现了发送给A的信息，那么立即会调用客户端的方法来推送信息到A。

二，建立Duplex模式的WCF服务

这里以一个简单的聊天功能来说明，WCF提供了三个方法，连接到服务器方法，发送信息方法和接收信息方法。从服务契约上来说分为两个接口，分别是为客户端提供发送信息和开始聊天方法的IChatService接口和服务器调用客户端方法的IChatServiceCallBack接口

IChatService.cs文件

代码

namespace ChatWCF 
{ 
     [ServiceContract(CallbackContract = typeof (IChatServiceCallBack))] // 这里需要定义IChatService接口的回调接口IChatServiceCallBack
    public   interface IChatService 
    { 
        [OperationContract] 
        bool SendMessage(MessageInfo msg); // 发送信息

        [OperationContract] 
        bool LoginChat( string User, string Partner); // 开始聊天模式  
    } 

    [ServiceContract] 
    public   interface IChatServiceCallBack //供 服务端回调的接口
    { 
        [OperationContract(IsOneWay = true )] 
        void ReceiveMessages(List < MessageInfo > listMessages); // 客户端被服务端回调后接收信息
    } 
}

 

接下来需要实现这接口，IChatService.svc.cs 

代码

namespace ChatWCF 
{ 
     public   class ChatService : IChatService 
     { 
        IChatServiceCallBack chatserviceCallBack; 
        string _user; 
        string _partner; 
　　　　 Timer timer;
// 开始聊天
public   bool LoginChat( string User, string Partner)

        { 
            try  
            { 
                chatserviceCallBack = OperationContext.Current.GetCallbackChannel < IChatServiceCallBack > (); 
                _user = User; 
                _partner = Partner;  

                timer =   new Timer( new TimerCallback(CheckMessages), this , 100 , 100 ); 

                return   true ; 
            } 
            catch (Exception ex) 
            { 
                return   false ; 
            } 
        } 
//检查消息并回调客户端接收此消息，此处是回调的重点
        private   void CheckMessages( object o)

        { 
            chatserviceCallBack.ReceiveMessages(GetMessages(_user,_partner)); 
        } 

// 发送信息
public   bool SendMessage(MessageInfo msg) 
{
                [ 将MessageInfo写入数据库...]  
} 

// 检测数据库
private List < MessageInfo > GetMessages( string User, string Partner) 
{ 
            List < MessageInfo > listMsg =   new List < MessageInfo > ();

   [检测数据库并返回检测到的MessageInfo...]      

    

            return listMsg; 
} 

// 执行简单的sql语句
private DataSet Excutesql( string strsql) 
       { 
            string strServer =   " server=LEON-PC\\sql2005;database=jplan;uid=sa;pwd=sa; " ; 
            sqlConnection con =   new sqlConnection(strServer); 
            con.open(); 
            sqlDataAdapter dataAdapter =   new sqlDataAdapter(strsql,con); 
            DataSet ds =   new DataSet(); 
            dataAdapter.Fill(ds); 
            con.Close(); 

            return ds; 
        } 
    } 
}

 

这里需要注意一点的是这个WCF是建立在Duplex基础上的，所以在wcf的项目中需要添加一个程序集：

Assembly System.ServiceModel.PollingDuplex
    C:\Program Files\Microsoft SDKs\Silverlight\v4.0\Libraries\Server\System.ServiceModel.PollingDuplex.dll

 

接下来需要对Web.config进行配置，主要是ServiceModel节点：

代码

< system.serviceModel >  
    < behaviors >  
      < serviceBehaviors >  
        < behavior name ="ChatWCF.ChatBehavior" >  
          < serviceMetadata httpGetEnabled ="true"   />  
          < serviceDebug includeExceptionDetailInFaults ="false"   />  
        </ behavior >  
      </ serviceBehaviors >  
    </ behaviors >  
    < services >  
      < service behaviorConfiguration ="ChatWCF.ChatBehavior" name ="ChatWCF.ChatService" >  
        < endpoint 
           address =""  
           binding ="pollingDuplexHttpBinding"  
           bindingConfiguration ="multipleMessagesPerPollPollingDuplexHttpBinding"  
           contract ="ChatWCF.IChatService" >  
        </ endpoint >  
        < endpoint 
            address ="mex"  
            binding ="mexHttpBinding"  
            contract ="IMetadataExchange" />  
      </ service >  
    </ services >  
    < extensions >  
      < bindingExtensions >  
        < add name = 
            "pollingDuplexHttpBinding"  
            type ="System.ServiceModel.Configuration.PollingDuplexHttpBindingCollectionElement,System.ServiceModel.PollingDuplex,Version=4.0.0.0,Culture=neutral,PublicKeyToken=31bf3856ad364e35"   />  
      </ bindingExtensions >  
    </ extensions >  

    < bindings >  
      < pollingDuplexHttpBinding >  
        < binding name ="multipleMessagesPerPollPollingDuplexHttpBinding"  
                 duplexMode ="MultipleMessagesPerPoll"  
                 maxOutputDelay ="00:00:07" />  
      </ pollingDuplexHttpBinding >
    </ bindings >  
    < serviceHostingEnvironment multipleSiteBindingsEnabled ="true"   />  
  </ system.serviceModel >  

 

如果您的WCF服务是一个单独的站点，而客户端是SL的话，鉴于SL的安全性考虑不支持跨域访问，那么就需要在WCF的根目录下放置一个XML策略文件，文件名为

clientaccesspolicy.xml：

代码

<? xml version="1.0" encoding="utf-8" ?>  
< access-policy >  
  < cross-domain-access >  
    < policy >  
      < allow-from http-request-headers ="SOAPAction" >  
        < domain uri ="*" />  
      </ allow-from >  
      < grant-to >  
        < resource path ="/" include-subpaths ="true" />  
      </ grant-to >  
    </ policy >  
  </ cross-domain-access >  
</ access-policy >

 如果您的配置和代码书写正确，浏览一下WCF服务会发现下图，说明服务已经正确host到VS的轻量级IIS上了

  

三，Silverlight跨域访问WCF的Duplex服务

先建立一个单独的project，silverlight app，当然还是需要先引用WCF服务的： 

  

新建一个SL文件，Chat.xaml代码，包括了一个发送消息窗口和一个显示聊天信息的窗口，这个聊天的窗口从普通HTML街面上接收两个参数，即user和partner互为聊天对象。

代码

< UserControl x:Class ="ChatSL.Chat"  
    xmlns ="http://schemas.microsoft.com/winfx/2006/xaml/presentation%22 
    xmlns:x=" http://schemas.microsoft.com/winfx/2006/xaml%22 
    xmlns:d ="http://schemas.microsoft.com/expression/blend/2008%22 
    xmlns:mc=" http://schemas.openxmlformats.org/markup-compatibility/2006%22 
    mc:Ignorable ="d"  
    d:DesignHeight ="510" d:DesignWidth ="514" >  

    < Grid x:Name ="LayoutRoot" Background ="White" Height ="479" Width ="485" >  
        < TextBox Height ="87" HorizontalAlignment ="Left" Margin ="12,347,0" Name ="txtMessage" VerticalAlignment ="Top" Width ="335"   />  
        < Button Content ="发送" Height ="29" HorizontalAlignment ="Right" Margin ="0,440,138,0" Name ="btnSend" VerticalAlignment ="Top" Width ="61" />  
        < ListBox Height ="317" HorizontalAlignment ="Left" ItemsSource =" {Binding MessageInfo,Mode=OneWay} " Name ="listMsgs" VerticalAlignment ="Top" Width ="335" Margin ="12,12,0" >  
            < ListBox.ItemTemplate >  
                < DataTemplate >  
                    < StackPanel Orientation ="Horizontal" >  
                        < TextBlock Text =" {Binding SendTime,StringFormat='HH:mm:ss'} "   ></ TextBlock >  
                        < TextBlock Text ="    "   ></ TextBlock >  
                        < TextBlock Text =" {Binding Sender} " Width ="60" ></ TextBlock >  
                        < TextBlock Text ="  :  "   ></ TextBlock >  
                        < TextBlock Text =" {Binding Message} " FontSize ="12" FontFamily ="Verdana" Foreground ="Chocolate" ></ TextBlock >  
                    </ StackPanel >  
                </ DataTemplate >  
            </ ListBox.ItemTemplate >  
        </ ListBox >  
        < Image Height ="31" HorizontalAlignment ="Left" Source ="Images/online.jpg" Margin ="351,0" Name ="image1" Stretch ="Fill" VerticalAlignment ="Top" Width ="32"   />  
        < Button Content ="关闭" Height ="29" HorizontalAlignment ="Left" Margin ="219,0" Name ="btnClose" VerticalAlignment ="Top" Width ="61"   />  
        < TextBox Height ="23" HorizontalAlignment ="Left" Margin ="389,17,0" Name ="txtPartner" VerticalAlignment ="Top" Width ="83"   />  
        < Image Height ="28" HorizontalAlignment ="Left" Margin ="352,0" Name ="image2" Source ="Images/online.jpg" Stretch ="Fill" VerticalAlignment ="Top" Width ="31"   />  
        < TextBox Height ="23" HorizontalAlignment ="Left" Margin ="389,349,0" Name ="txtMe" VerticalAlignment ="Top" Width ="83"   />  
    </ Grid >  
</ UserControl >

 

后台代码中需要从HTML中接收聊天对象:

代码

namespace ChatSL 
{ 
    public   partial   class Chat : UserControl 
    {  
        string user; 
        string partner; 

        EndpointAddress address ; 
        PollingDuplexHttpBinding binding; 
        ChatService.ChatServiceClient proxy; 

        public Chat() 
        { 
            InitializeComponent();

            this .Loaded += new RoutedEventHandler(Chat_Loaded); 
            this .txtMessage.KeyDown +=   new KeyEventHandler(KeyDownProcess); 
            this .btnSend.Click +=   new RoutedEventHandler(btnSend_Click); 
            this .btnClose.Click +=   new RoutedEventHandler(btnClose_Click); 
        } 

        void Chat_Loaded( object sender,RoutedEventArgs e) 
        { 
            HtmlElement element; 
            element = HtmlPage.Document.GetElementById( " lbluser " ); 
            this .txtMe.Text = element.GetAttribute( " innerText " ); 
            element = HtmlPage.Document.GetElementById( " lblpartner " ); 
            this .txtPartner.Text = element.GetAttribute( " innerText " ); 

            user =   this .txtMe.Text; 
            partner =   this .txtPartner.Text; 

            LogIn(); 
        } 
//向服务器示意上线
        private   void LogIn() 
        { 
            address =   new EndpointAddress( " http://localhost:32662/ChatService.svc%22);
            binding =   new PollingDuplexHttpBinding(PollingDuplexMode.MultipleMessagesPerPoll); 
            proxy =   new ChatService.ChatServiceClient(binding,address); 
            proxy.ReceiveMessagesReceived += new EventHandler < ChatService.ReceiveMessagesReceivedEventArgs > (proxy_ReceiveMessagesReceived); 
            proxy.LoginChatAsync(user,partner); 
        } 

        #region 绑定数据
        void proxy_ReceiveMessagesReceived( object sender,ChatService.ReceiveMessagesReceivedEventArgs e) 
        { 
            this .listMsgs.ItemsSource = e.listMessages; 
        } 

        private   void SetDataSource() 
        { 
            
        } 
        #endregion  

        #region 键盘事件
        protected   void KeyDownProcess( object sender,KeyEventArgs e) 
        { 
            if (e.Key == Key.Enter) 
            { 
                SendMessage(); 
            } 
        } 
        #endregion  

        #region   发送信息
        private   void btnSend_Click( object sender,RoutedEventArgs e) 
        { 
            SendMessage(); 
        } 
        private   void SendMessage() 
        { 
            if ( this .txtMessage.Text ==   "" ) 
            { 
                MessageBox.Show( " 请输入信息！ " ); 
                return ; 
            } 

            ChatService.MessageInfo message =   new ChatService.MessageInfo(); 
            message.ID = Guid.NewGuid().ToString(); 
            message.Receipt =   0 ; 
            message.ReceiveMode =   " user " ; 
            message.ReceiveOrgan =   "" ; 
            message.ReceiveUser =   this .txtPartner.Text; 
            message.Message =   this .txtMessage.Text; 
            message.Sender =   this .txtMe.Text; 
            message.SendTime = DateTime.Now; 
            message.source =   " web " ; 
            message.State =   0 ; 
            message.Title =   this .txtMessage.Text; 

            proxy =   new ChatService.ChatServiceClient(binding,address); 
            proxy.SendMessageCompleted  +=   new EventHandler < ChatService.SendMessageCompletedEventArgs > (SendMessageComleted); 
            proxy.SendMessageAsync(message); 

            this .txtMessage.Text =   "" ; 
        } 
        void SendMessageComleted( object sender,ChatService.SendMessageCompletedEventArgs e) 
        { 
            if (e.Error ==   null ) 
            { 
                // MessageBox.Show(e.Result.ToString());
            } 
        } 
        #endregion  

        #region 关闭窗口
        private   void btnClose_Click( object sender,EventArgs e) 
        { 

        } 
        #endregion  
    } 
}

效果图：