WCF Service Contract之MEPs
LazyBee
WCF支持的消息交换模式MEPs(Message Exchange Partten)为三种：请求-响应模式（Request-Replay）， 单向模式(One Way)，双向模式（Duplex）.
[ServiceContract(SessionMode=SessionMode.Required)]
public interface ICalculatorSession
{
[OperationContract(IsOneWay = true)]
void AddTo(double n);
[OperationContract]
double Equals();
}
以上AddTo方法就是单向模式，而Equals就是双向模式。（缺省的IsOneWay的值是false）
缺省的消息交换模式就是Request-Replay模式。
注意：如果指定的方法的消息交换模式是One Way,那么这个方法的返回值必须是void，并且不能有out和ref的参数。当WCF服务的客户端不应该等到对应的操作的完成并且也不需要处理SOAP错误时，采用这种单向模式。（这个方法的返回值是void并不代表该方法会返回消息给调用者。）
Duplex模式是客户端和服务之间可以相互独立的使用One Way和Request-Replay进行双向通讯的消息交换模式。
在使用Duplex进行消息交换的时候，并且客户端调用的是定义为Request-Reply的服务操作，而且在这个服务操作中又调用客户端的另外一个Request-Reply的一个回调方法，这时就会遇到如下错误，你可以根据提示进行修复操作。
错误：This operation would deadlock because the reply cannot be received until the current Message completes processing. If you want to allow out-of-order message processing, specify ConcurrencyMode of Reentrant（可重入的并发模式） or Multiple on ServiceBehaviorAttribute.
//服务器端代码=================================================================using System;using System.ServiceModel;namespace Microsoft.ServiceModel.Samples
{
// Define a duplex service contract. // A duplex contract consists of two interfaces. // The primary interface is used to send messages from the client to the service. // The callback interface is used to send messages from the service back to the client. // ICalculatorDuplex allows one to perform multiple operations on a running result. // The result is sent back after each operation on the ICalculatorCallback interface. [ServiceContract(Namespace = "http://Microsoft.ServiceModel.Samples", SessionMode=SessionMode.Required, CallbackContract=typeof(ICalculatorDuplexCallback))] 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); [OperationContract] String Request_ReplayMethodInDuplex(int i);
} // The callback interface is used to send messages from service back to client. // The Result operation will return the current result after each operation. // The Equation opertion will return the complete equation after Clear() is called. public interface ICalculatorDuplexCallback { [OperationContract(IsOneWay = true)] void Result(double result); [OperationContract(IsOneWay = true)] void Equation(string eqn); [OperationContract(IsOneWay=true)] void ShowMessage(string s); } // Service class which implements a duplex service contract. // Use an InstanceContextMode of PerSession to store the result // An instance of the service will be bound to each duplex session [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 { get { return OperationContext.Current.GetCallbackChannel<ICalculatorDuplexCallback>(); } } public string Request_ReplayMethodInDuplex(int i) { Callback.ShowMessage("Hello World!" + i); return "hello world " + i; } }
}
//Web.Config的内容===============================================================================================================<?xml version="1.0" encoding="utf-8" ?><configuration> <system.serviceModel> <services> <service name="Microsoft.ServiceModel.Samples.CalculatorService" behaviorConfiguration="CalculatorServiceBehavior"> <!-- 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="True" /> </behavior> </serviceBehaviors> </behaviors> </system.serviceModel> <system.web> <compilation debug="true"/> </system.web></configuration>//Service.svc的内容
===================================================================================
<%@ServiceHost language=c# Debug="true" Service="Microsoft.ServiceModel.Samples.CalculatorService" %>
1 首先在IIS中创建一个http://localhost/servicemodelsamples的虚拟目录。
2 如果你是第一次运行WCF Service的话，需要将.svc扩展名和aspnet_isapi.dll关联，具体操作如下：
1. 打开IIS管理器.
2. 右单击 Web Sites 并且选择属性 Properties.
3. On the Home Directory tab, click 配置Configuration.
4. In the list of application mappings, verify that the .svc file is mapped to the aspnet_isapi.dll. If the file has not been mapped:
a. 单击增加按钮.
b. 在 Add/Edit Application Extension Mapping 对话框中, 单击浏览按钮
c. 找到aspnet_isapi.dll并单击Open.
d. 制定 .svc 扩展名
e. 确保Check that file exists 选项没有被选中.
f. 单击确定, 然后再单击确定回到站点属性窗口.
5. 单击确定关闭站点属性窗口。
3然后就可以在IE窗口中测试时候正常运行了。（http://localhost/servicemodelsamples/service.svc）.
由于VS2008自带的WCFTestClient.exe不能测试duplex模式的WCF Service，所以必须手动来产生客户端测试，为了方便应对服务契约的变更，可以在client 的项目属性的Build Events中的Pre-Build event command line的文本框中增加如下命令以帮助自动生成客户端的代理类：
Call "D:\Program Files\Microsoft Visual Studio 9.0\VC\vcvarsall.bat" x86
svcutil /language:cs /noconfig /out:$(ProjectDir)generatedClient.cs /n:*,Microsoft.ServiceModel.Samples http://localhost/servicemodelsamples/service.svc?wsdl
============================================================================================================
using System;using System.ServiceModel;namespace Microsoft.ServiceModel.Samples{ // The service contract is defined in generatedClient.cs, generated from the service by the svcutil tool. // Define class which implements callback interface of duplex contract public class CallbackHandler : ICalculatorDuplexCallback { public void Result(double result) { Console.WriteLine("Result({0})", result); } public void Equation(string eqn) { Console.WriteLine("Equation({0})", eqn); } public void ShowMessage(string s) { Console.WriteLine("ZXG:" + s); } } class Client { 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.WriteLine(client.Request_ReplayMethodInDuplex(2)); //Closing the client gracefully closes the connection and cleans up resources client.Close(); Console.ReadLine(); } }}以下是客户端的配置文件：
<?xml version="1.0" encoding="utf-8" ?><configuration> <system.serviceModel> <client> <endpoint name="" address="http://localhost/servicemodelsamples/service.svc" binding="wsDualHttpBinding" bindingConfiguration="DuplexBinding" contract="Microsoft.ServiceModel.Samples.ICalculatorDuplex" /> </client> <bindings> <!-- configure a binding that support duplex communication --> <wsDualHttpBinding> <binding name="DuplexBinding" clientBaseAddress="http://localhost:8000/myClient/"> </binding> </wsDualHttpBinding> </bindings> </system.serviceModel></configuration>This operation would deadlock because the reply cannot be received until the current Message completes processing. If you want to allow out-of-order message processing, specify ConcurrencyMode of Reentrant（可重入的并发模式） or Multiple on ServiceBehaviorAttribute.