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 ="12,347,0,0"  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 ="12,12,0,0" >   
             < 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 ="351,12,0,0"  Name ="image1"  Stretch ="Fill"  VerticalAlignment ="Top"  Width ="32"   />   
         < Button  Content ="关闭"  Height ="29"  HorizontalAlignment ="Left"  Margin ="219,440,0,0"  Name ="btnClose"  VerticalAlignment ="Top"  Width ="61"   />   
         < TextBox  Height ="23"  HorizontalAlignment ="Left"  Margin ="389,17,0,0"  Name ="txtPartner"  VerticalAlignment ="Top"  Width ="83"   />   
         < Image  Height ="28"  HorizontalAlignment ="Left"  Margin ="352,347,0,0"  Name ="image2"  Source ="Images/online.jpg"  Stretch ="Fill"  VerticalAlignment ="Top"  Width ="31"   />   
         < TextBox  Height ="23"  HorizontalAlignment ="Left"  Margin ="389,349,0,0"  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： 

     本文转自wengyuli 51CTO博客，原文链接：http://blog.51cto.com/wengyuli/587835，如需转载请自行联系原作者