WCF消息交换模式之Duplex

WCF消息交换模式有三种：request/reply，oneWay 和duplex
前两个看看就明白怎么回事。duplex是最复杂的一个，官方文档介绍比较多的一个。
duplex：双方的，相互的意思
duplex格式的契约允许客户端和服务器彼此独立的交流。
duplex是由在客户端和服务器端的两个IsOneWay的契约组成的。
实现方法主要是
在服务器端有两个契约接口：（两个接口都在服务端放置）
一个是由服务端实现来作为服务端类被客户端调用，这就是和前面两个消息交换模式一样的方法。
一个是在客户端实现的接口但被服务端调用的类。
通过这两个接口来实现服务端和客户端的相互交流

简单的代码实现（vs2005 ，控制台应用程序）
服务端代码：
这是两个接口类代码：
&<60;[ServiceContract(Namespace = "http://Microsoft.ServiceModel.Samples", SessionMode = SessionMode.Required,CallbackContract = typeof(ICalculatorDuplexCallback))]//注意这里面的参数配置
public interface ICalculatorDuplex
{
[OperationContract(IsOneWay = true)]
void Clear();
[OperationContract(IsOneWay = true)]
void AddTo(double n);
[OperationContract(IsOneWay = true)]
void SubtractFrom(double n);
[OperationContract(IsOneWay = true)]
void MultiplyBy(double n);
[OperationContract(IsOneWay = true)]
void DivideBy(double n);
}

public interface ICalculatorDuplexCallback//这个接口不会在服务器被实现，而是在客户端实现
{
[OperationContract(IsOneWay = true)]
void Result(double result);
[OperationContract(IsOneWay = true)]
void Equation(string eqn);
}
服务端实现的接口
&<60;[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession)]
public class CalculatorService : ICalculatorDuplex
{
double result = 0.0D;
string equation;

public CalculatorService()
{
equation = result.ToString();
}

public void Clear()
{

Callback.Equation(equation + " = " + result.ToString());
equation = result.ToString();
}

public void AddTo(double n)
{
result += n;
equation += " + " + n.ToString();
Callback.Result(result);
}

public void SubtractFrom(double n)
{
result -= n;
equation += " - " + n.ToString();
Callback.Result(result);
}

public void MultiplyBy(double n)
{
result *= n;
equation += " * " + n.ToString();
Callback.Result(result);
}

public void DivideBy(double n)
{
result /= n;
equation += " / " + n.ToString();
Callback.Result(result);
}

ICalculatorDuplexCallback Callback//实例接口
{
get
{
return OperationContext.Current.GetCallbackChannel<ICalculatorDuplexCallback>();
}
}
服务端的配置文件：
<?xml version="1.0" encoding="utf-8" ?>
<configuration>

<system.serviceModel>
<services>
<service
name="Microsoft.ServiceModel.Samples.CalculatorService"
behaviorConfiguration="CalculatorServiceBehavior">
<host>
<baseAddresses>
<add baseAddress="http://localhost/servicemodelsamples/service.svc "/>
</baseAddresses>
</host>
<!-- This endpoint is exposed at the base address provided by host: http://localhost/servicemodelsamples/service.svc -->
<endpoint address=""
binding="wsDualHttpBinding"
contract="Microsoft.ServiceModel.Samples.ICalculatorDuplex" />
<!-- the mex endpoint is exposed at http://localhost/servicemodelsamples/service.svc/mex -->
<endpoint address="mex"
binding="mexHttpBinding"
contract="IMetadataExchange" />
</service>
</services>

<!--For debugging purposes set the includeExceptionDetailInFaults attribute to true-->
<behaviors>
<serviceBehaviors>
<behavior name="CalculatorServiceBehavior">
<serviceMetadata httpGetEnabled="True"/>
<serviceDebug includeExceptionDetailInFaults="False" />
</behavior>
</serviceBehaviors>
</behaviors>

</system.serviceModel>

</configuration>
编译运行，然后svctuil工具生成代码，可以参考上一篇文章。
在客户端代码：
在这个地方实现在服务端的接口
public class CallbackHandler : ICalculatorDuplexCallback
{
public void Result(double result)
{
Console.WriteLine("Result({0})", result);
}

public void Equation(string eqn)
{
Console.WriteLine("Equation({0})", eqn);
}
}
main函数的方法：

static void Main()
{
// Construct InstanceContext to handle messages on callback interface
InstanceContext instanceContext = new InstanceContext(new CallbackHandler());

// Create a client
CalculatorDuplexClient client = new CalculatorDuplexClient(instanceContext);

Console.WriteLine("Press <ENTER> to terminate client once the output is displayed.");
Console.WriteLine();

// Call the AddTo service operation.
double value = 100.00D;
client.AddTo(value);

// Call the SubtractFrom service operation.
value = 50.00D;
client.SubtractFrom(value);

// Call the MultiplyBy service operation.
value = 17.65D;
client.MultiplyBy(value);

// Call the DivideBy service operation.
value = 2.00D;
client.DivideBy(value);

// Complete equation
client.Clear();

Console.ReadLine();

//Closing the client gracefully closes the connection and cleans up resources
client.Close();
}
可以参考msdn相关资源

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