彩票走势图

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

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

namespace ChatWCF
{
public class ChatService : IChatService
{
IChatServiceCallBack chatserviceCallBack;
string _user;
string _partner;

//开始聊天
public bool LoginChat(string User, string Partner)

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

Timer 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：

<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：

<?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。

<UserControl x:Class="ChatSL.Chat"
xmlns="//schemas.microsoft.com/winfx/2006/xaml/presentation%22
xmlns:x="//schemas.microsoft.com/winfx/2006/xaml%22
xmlns:d="//schemas.microsoft.com/expression/blend/2008%22
xmlns:mc="//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:

#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：