[原创]WCF后续之旅(2): 如何对Channel Layer进行扩展——创建自定义Channel

在上一篇文章中，我们通过一个直接借助BasicHttpBinding对象实现Client和Server端进行通信的例子，对WCF channel layer进行了一个大致上的介绍。由此引出了一些列通信相关的概念和对象，比如Channel，Output channel， Input channel，Request channel, Reply Channel，Duplex channel， Channel Shape，Channel manager，Channel factory, Channel listener, Binding element 等。通过这些元素，我们很容易地实现对WCF channel layer进行扩展。

对channel layer进行扩展一般适用于当你的需求通过现有的Binding，或者channel不能实现，而需要自定义一些channel来实现你所需的功能。不如现在的WCF系统定义的Channel中没有实现对Message body的压缩功能。你可以就需要将此功能定义到一个custom channel中，然后将其注入到channel stack中。一般来说，仅仅创建custom channel是不够的，因为在runtime， channel是通过Channel manager进行创建的，所以你需要创建对应的Channel factory（如何对发送方进行扩展）或者Channel listener（如果对接受方进行扩展）。而Channel factory和channel listener最终又是通过Binding element进行创建的，所以你还需要创建相应的Binding element。（Binding element=〉Channel factory&Channel listener=>Channel）

在本章节中，我们将继续讨论WCF channel layer。我们将通过如何创建和应用custom channel来介绍channel layer一些知识。

1、ICommunicationObject 和 CommunicationObject

我们知道WCF channel layer的绝大部分对象，比如Channel，Channel factory，Channel listener，从功能上讲都是用于通信（Communication）的对象，对传统的communication object，比如socket，他们往往都具有通过状态和状态转化规则（状态机：State machine）。这些状态包括Creating、Created、Opening、Opened、Closing、Closed等等。为了统一管理这些状态和状态之间的转化，WCF定义个一个特殊的Interface：ICommunicationObject

public interface ICommunicationObject
{
    // Events
    event EventHandler Closed;
    event EventHandler Closing;
    event EventHandler Faulted;
    event EventHandler Opened;
    event EventHandler Opening;

    // Methods
    void Abort();
    IAsyncResult BeginClose(AsyncCallback callback, object state);
    IAsyncResult BeginClose(TimeSpan timeout, AsyncCallback callback, object state);
    IAsyncResult BeginOpen(AsyncCallback callback, object state);
    IAsyncResult BeginOpen(TimeSpan timeout, AsyncCallback callback, object state);
    void Close();
    void Close(TimeSpan timeout);
    void EndClose(IAsyncResult result);
    void EndOpen(IAsyncResult result);
    void Open();
    void Open(TimeSpan timeout);

    // Properties
    CommunicationState State { get; }
} 

ICommunicationObject定义了3种成员：

• Property：State， 得到当前的状态，返回值是一个CommunicationState  枚举。
• Method：同步、异步Open和Close方法。
• Event：通过注册这些状态相关的Event，当时对象转化到对应的状态时执行相应操作。

WCF定义了一个abstract class: CommunicationObject直接实现了该Interface。CommunicationObject的实现统一的State machine。WCF channel layer的很多的class都直接或者间接的继承了这个class。你也可以让你的class继承该class。当你让你自己的class继承CommunicationObject的时候，在override 掉base相应的method的时候，强烈建议你先调用base对应的方法，CommunicationObject会帮你进行相应的State转换和触发相应的事件。

2. Channel 和Channel Shape

在上一篇文章中，我们讨论过了。在不同的消息交换模式（MEP）中，发送方和接受方的Channel扮演的角色是不相同的。我们并把这种不同MEP中消息交互双方Channel的结构差异表述为Channel shape。我们有四种不同的Channel shape：Datagram、Request/reply、Duplex和P2P。不同Channel shape中Channel的结构性差性通过实现不同的Channel interface来体现。

对于Datagram channel shape，采用了One-way的MEP。发送方的channel 必须实现IOutputChannel interface。该Interface的方法成员主要集中在用于发送message的Send方法（同步/异步）：

 

public interface IOutputChannel : IChannel, ICommunicationObject
{
    // Methods
    IAsyncResult BeginSend(Message message, AsyncCallback callback, object state);
    IAsyncResult BeginSend(Message message, TimeSpan timeout, AsyncCallback callback, object state);
    void EndSend(IAsyncResult result);
    void Send(Message message);
    void Send(Message message, TimeSpan timeout);

    // Properties
    EndpointAddress RemoteAddress { get; }
    Uri Via { get; }
} 

与之相应是IInputChannel inteface，该Interface用于Datagram channel shape中接收方的channel定义。其主要方法成员主要集中在用于接收Message的Receive方法（同步/异步）：

public interface IInputChannel : IChannel, ICommunicationObject
{
    // Methods
    IAsyncResult BeginReceive(AsyncCallback callback, object state);
    IAsyncResult BeginReceive(TimeSpan timeout, AsyncCallback callback, object state);
    IAsyncResult BeginTryReceive(TimeSpan timeout, AsyncCallback callback, object state);
    IAsyncResult BeginWaitForMessage(TimeSpan timeout, AsyncCallback callback, object state);
    Message EndReceive(IAsyncResult result);
    bool EndTryReceive(IAsyncResult result, out Message message);
    bool EndWaitForMessage(IAsyncResult result);
    Message Receive();
    Message Receive(TimeSpan timeout);
    bool TryReceive(TimeSpan timeout, out Message message);
    bool WaitForMessage(TimeSpan timeout);

    // Properties
    EndpointAddress LocalAddress { get; }
} 

 注：无论对于同步或者异步方法，一般由两个重载，一个接收一个TimeSpan 作为参数，表是Send或者Receive允许的时间范围。而另一个没有该参数的方式，不不是建议你使用一个无限的TimeSpan，而是使用一个可配置的默认时间段（实际上是Binding对象对应的属性）

不同于Datagram channel shape，Request/request channel shape下交互双方的Channel具有不同的行为。发送方的Channel实现IRequestChannel。该interface的方面成员主要集中在一些用于向接收方进行请求的Request方法（同步/异步）：上面。

 

public interface IRequestChannel : IChannel, ICommunicationObject
{
    // Methods
    IAsyncResult BeginRequest(Message message, AsyncCallback callback, object state);
    IAsyncResult BeginRequest(Message message, TimeSpan timeout, AsyncCallback callback, object state);
    Message EndRequest(IAsyncResult result);
    Message Request(Message message);
    Message Request(Message message, TimeSpan timeout);

    // Properties
    EndpointAddress RemoteAddress { get; }
    Uri Via { get; }
} 

同理，对于接收方的IReplyChannel则主要定义了一些用于Reply的方法：

public interface IReplyChannel : IChannel, ICommunicationObject
{
    // Methods
    IAsyncResult BeginReceiveRequest(AsyncCallback callback, object state);
    IAsyncResult BeginReceiveRequest(TimeSpan timeout, AsyncCallback callback, object state);
    IAsyncResult BeginTryReceiveRequest(TimeSpan timeout, AsyncCallback callback, object state);
    IAsyncResult BeginWaitForRequest(TimeSpan timeout, AsyncCallback callback, object state);
    RequestContext EndReceiveRequest(IAsyncResult result);
    bool EndTryReceiveRequest(IAsyncResult result, out RequestContext context);
    bool EndWaitForRequest(IAsyncResult result);
    RequestContext ReceiveRequest();
    RequestContext ReceiveRequest(TimeSpan timeout);
    bool TryReceiveRequest(TimeSpan timeout, out RequestContext context);
    bool WaitForRequest(TimeSpan timeout);

    // Properties
    EndpointAddress LocalAddress { get; }
}

而对与Duplex和P2P，消息交互双方使用相同的Channel：Duplex channel。本质上讲，DuplexChannel = OutputChannel + IntputChannel。这一点从IDuplexChannel的定义上就可以看出来：

public interface IDuplexChannel : IInputChannel, IOutputChannel, IChannel, ICommunicationObject
{
} 

3、创建Custom Channel

为了让大家对WCF channel layer有一个深刻的认识，以及掌握如何有效地对其进行扩展。我在整篇文章中穿插介绍一个具体的Sample：创建一个自定义的channel，以及相关的辅助对象，比如Channel factory、Channel listener和Binding element。

这个Sample将基于我们最为常用的Request/Reply channel shape。所以我们需要创建两个Channel，一个是用于发送方的实现了IRequestChannel的Channel，而另一个则是实现了IReplyChannel的用于接收方的Channel。

为了简单起见，在我定义的channel的每个方法仅仅打印出相应的方法名称而已（这样做不但简单，还有的一个好处，那就是当我最后将其应用到具体的Messaging场景中，可以根据控制台打印出来的文字清楚地看清当我们的Channel应用到具体的场景中后先后执行了那些方法）。

我们先来看看实现了IRequestChannel的MyRequestChannel的定义：

namespace Artech.ChannleStackExplore.Channels
{
    public class MyRequestChannel :ChannelBase, IRequestChannel
    {
        private IRequestChannel InnerChannel
        {get;set;} 

        public MyRequestChannel(ChannelManagerBase channleManager, IRequestChannel innerChannel)
            : base(channleManager)
        {
            this.InnerChannel = innerChannel;
        } 

        ChannelBase Members#region ChannelBase Members
        protected override void OnAbort()
        {
            Console.WriteLine("MyRequestChannel.OnAbort()");
            this.InnerChannel.Abort();
        } 

        protected override IAsyncResult OnBeginClose(TimeSpan timeout, AsyncCallback callback, object state)
        {
            Console.WriteLine("MyRequestChannel.OnBeginClose()");
            return this.InnerChannel.BeginClose(timeout, callback, state);
        } 

        protected override IAsyncResult OnBeginOpen(TimeSpan timeout, AsyncCallback callback, object state)
        {
            Console.WriteLine("MyRequestChannel.OnBeginOpen()");
            return this.InnerChannel.BeginOpen(timeout, callback, state);
        } 

        protected override void OnClose(TimeSpan timeout)
        {
            Console.WriteLine("MyRequestChannel.OnClose()");
            this.Close(timeout);
        } 

        protected override void OnEndClose(IAsyncResult result)
        {
            Console.WriteLine("MyRequestChannel.OnEndClose()");
            this.InnerChannel.EndClose(result);
        } 

        protected override void OnEndOpen(IAsyncResult result)
        {
            Console.WriteLine("MyRequestChannel.OnEndOpen()");
            this.InnerChannel.EndOpen(result);
        } 

        protected override void OnOpen(TimeSpan timeout)
        {
            Console.WriteLine("MyRequestChannel.OnOpen()");
            this.InnerChannel.Open(timeout);
        }
        #endregion 

        IRequestChannel Members#region IRequestChannel Members

        public IAsyncResult BeginRequest(Message message, TimeSpan timeout, AsyncCallback callback, object state)
        {
            Console.WriteLine("MyRequestChannel.BeginRequest()");
            return this.BeginRequest(message, timeout, callback, state);
        } 

        public IAsyncResult BeginRequest(Message message, AsyncCallback callback, object state)
        {
            Console.WriteLine("MyRequestChannel.BeginRequest()");
            return this.InnerChannel.BeginRequest(message, callback, state);
        } 

        public Message EndRequest(IAsyncResult result)
        {
            Console.WriteLine("MyRequestChannel.EndRequest()");
            return this.InnerChannel.EndRequest(result);
        } 

        public EndpointAddress RemoteAddress
        {
            get 
            {
                Console.WriteLine("MyRequestChannel.RemoteAddress");
                return this.InnerChannel.RemoteAddress;
            } 

        } 

        public Message Request(Message message, TimeSpan timeout)
        {
            Console.WriteLine("MyRequestChannel.Request()");
            return this.InnerChannel.Request(message, timeout);
        } 

        public Message Request(Message message)
        {
            Console.WriteLine("MyRequestChannel.Request()");
            return this.InnerChannel.Request(message);
        } 

        public Uri Via
        {
            get 
            {
                Console.WriteLine("MyRequestChannel.Via)");
                return this.InnerChannel.Via;
            } 

        } 

        #endregion
    }
} 

这里唯一需要注意的一点是：在实际的运行环境中，我们的channel仅仅了位于Channel stack的某个环节。该channel和其他的一些channel组成一个管道，这个管道里流淌是Message。所以当一个Channel执行了它相应的操作的时候，需要将message传到下一个channel作进一步处理。所有我们的Channel需要下一个Channel的应用，这个Channel就是我们的InnerChannel字段，该成员在构造函数中指定。

 

private IRequestChannel InnerChannel
{get;set;} 

public MyRequestChannel(ChannelManagerBase channleManager, IRequestChannel innerChannel)
            : base(channleManager)
{
    this.InnerChannel = innerChannel;
} 

所以，对于每一个方法，在实现了本Channel的功能之后，只需要调用InnerChannel 的对应的方法即可。

我们再来看看实现了IReplyChannel的MyReplyChannel， 它用于接收方：

 

namespace Artech.ChannleStackExplore.Channels
{
    public class MyReplyChannel: ChannelBase, IReplyChannel
    {
        private IReplyChannel InnerChannel
        { get; set; } 

        public MyReplyChannel(ChannelManagerBase channelManager, IReplyChannel innerChannel):base(channelManager)
        {
            this.InnerChannel = innerChannel;
        } 

        ChannelBase Members#region ChannelBase Members
        protected override void OnAbort()
        {
            Console.WriteLine("MyReplyChannel.OnAbort()");
            this.InnerChannel.Abort();
        } 

        protected override IAsyncResult OnBeginClose(TimeSpan timeout, AsyncCallback callback, object state)
        {
            Console.WriteLine("MyReplyChannel.OnBeginClose()");
            return this.InnerChannel.BeginClose(timeout, callback, state);
        } 

        protected override IAsyncResult OnBeginOpen(TimeSpan timeout, AsyncCallback callback, object state)
        {
            Console.WriteLine("MyReplyChannel.OnBeginOpen()");
            return this.InnerChannel.BeginOpen(timeout, callback, state);
        } 

        protected override void OnClose(TimeSpan timeout)
        {
            Console.WriteLine("MyReplyChannel.OnClose()");
            this.Close(timeout);
        } 

        protected override void OnEndClose(IAsyncResult result)
        {
            Console.WriteLine("MyReplyChannel.OnEndClose()");
            this.InnerChannel.EndClose(result);
        } 

        protected override void OnEndOpen(IAsyncResult result)
        {
            Console.WriteLine("MyReplyChannel.OnEndOpen()");
            this.InnerChannel.EndOpen(result);
        } 

        protected override void OnOpen(TimeSpan timeout)
        {
            Console.WriteLine("MyReplyChannel.OnOpen()");
            this.InnerChannel.Open(timeout);
        }
        #endregion 

        IReplyChannel Members#region IReplyChannel Members

        public IAsyncResult BeginReceiveRequest(TimeSpan timeout, AsyncCallback callback, object state)
        {
            Console.WriteLine("MyReplyChannel.BeginReceiveRequest()");
            return this.InnerChannel.BeginReceiveRequest(timeout, callback, state);
        } 

        public IAsyncResult BeginReceiveRequest(AsyncCallback callback, object state)
        {
            Console.WriteLine("MyReplyChannel.BeginReceiveRequest()");
            return this.InnerChannel.BeginReceiveRequest(callback, state);
        } 

        public IAsyncResult BeginTryReceiveRequest(TimeSpan timeout, AsyncCallback callback, object state)
        {
            Console.WriteLine("MyReplyChannel.BeginTryReceiveRequest()");
            return this.InnerChannel.BeginTryReceiveRequest(timeout, callback, state);
        } 

        public IAsyncResult BeginWaitForRequest(TimeSpan timeout, AsyncCallback callback, object state)
        {
            Console.WriteLine("MyReplyChannel.BeginWaitForRequest()");
            return this.InnerChannel.BeginWaitForRequest(timeout, callback, state);
        } 

        public RequestContext EndReceiveRequest(IAsyncResult result)
        {
            Console.WriteLine("MyReplyChannel.EndReceiveRequest()");
            return this.InnerChannel.EndReceiveRequest(result);
        } 

        public bool EndTryReceiveRequest(IAsyncResult result, out RequestContext context)
        {
            Console.WriteLine("MyReplyChannel.EndTryReceiveRequest()");
            return this.InnerChannel.EndTryReceiveRequest(result, out context);
        } 

        public bool EndWaitForRequest(IAsyncResult result)
        {
            Console.WriteLine("MyReplyChannel.EndWaitForRequest()");
            return this.InnerChannel.EndWaitForRequest(result);
        } 

        public System.ServiceModel.EndpointAddress LocalAddress
        {
            get 
            {
                Console.WriteLine("MyReplyChannel.LocalAddress");
                return this.InnerChannel.LocalAddress;
            }
        } 

        public RequestContext ReceiveRequest(TimeSpan timeout)
        {
            Console.WriteLine("MyReplyChannel.ReceiveRequest()");
            return this.InnerChannel.ReceiveRequest(timeout);
        } 

        public RequestContext ReceiveRequest()
        {
            Console.WriteLine("MyReplyChannel.ReceiveRequest()");
            return this.InnerChannel.ReceiveRequest();
        } 

        public bool TryReceiveRequest(TimeSpan timeout, out RequestContext context)
        {
            Console.WriteLine("MyReplyChannel.TryReceiveRequest()");
            return this.InnerChannel.TryReceiveRequest(timeout, out context);
        } 

        public bool WaitForRequest(TimeSpan timeout)
        {
            Console.WriteLine("MyReplyChannel.WaitForRequest()");
            return this.InnerChannel.WaitForRequest(timeout);
        } 

        #endregion
    }
} 

MyReplyChannel的定义方式和MyRequestChannel完全一样，我们就不用再多说什么了。

4. 创建Custom Channel Factory & Channel Listener

通过上一篇文章的介绍，我们知道Channel是通过Channel Manager来创建并管理的，在发送方的Channel Manager被称为Channel Factory。

对于Channel factory，除了定义了两个Interface之外（IChannelFactory 和IChannelFactory<TChannel>）

 

public interface IChannelFactory : ICommunicationObject
   {
       // Methods
       T GetProperty<T>() where T : class;
   } 




public interface IChannelFactory<TChannel> : IChannelFactory, ICommunicationObject
{
    // Methods
    TChannel CreateChannel(EndpointAddress to);
    TChannel CreateChannel(EndpointAddress to, Uri via);
} 

还定义了两个Base class：ChannelFactoryBase 和ChannelFactoryBase<TChannel>（限于篇幅，在这里就不多作介绍了）。

为了简单起见，我们上我们的Channel factory继承自ChannelFactoryBase<TChannel>：

namespace Artech.ChannleStackExplore.Channels
{
    public class MyChannelFactory<TChannel> : ChannelFactoryBase<TChannel>
    {
        private IChannelFactory<TChannel> InnerChannelFactory
        { get; set; } 

        public MyChannelFactory(BindingContext context)
        {
            this.InnerChannelFactory = context.BuildInnerChannelFactory<TChannel>();
        } 

        protected override TChannel OnCreateChannel(EndpointAddress address, Uri via)
        {
            Console.WriteLine("MyChannelFactory<TChannel>.OnClose()");
            TChannel innerChannel = this.InnerChannelFactory.CreateChannel(address, via);
            return (TChannel)(object)(new MyRequestChannel(this, innerChannel as IRequestChannel));
        } 

        protected override IAsyncResult OnBeginOpen(TimeSpan timeout, AsyncCallback callback, object state)
        {
            Console.WriteLine("MyChannelFactory<TChannel>.OnBeginOpen()");
            return this.InnerChannelFactory.BeginOpen(timeout, callback, state);
        } 

        protected override void OnEndOpen(IAsyncResult result)
        {
            Console.WriteLine("MyChannelFactory<TChannel>.OnEndOpen()");
            this.InnerChannelFactory.EndOpen(result);
        } 

        protected override void OnOpen(TimeSpan timeout)
        {
            Console.WriteLine("MyChannelFactory<TChannel>.OnOpen()");
            this.InnerChannelFactory.Open();
        }
    }
} 

我们说过，和Channel stack一样，Channel factory仍然是一个stack，原因很简单，一个个的Channel需要相应的channel factory来创建。同Channel一样，当channel factory创建了自己的channel之后需要将接力棒交到下一个Channel factory。不过不通于Channel的是，下一个Channel factory不时在构造函数直接指定的，而是通过构造函数中的BindingContext 对象的BuildInnerChannelFactory()创建。

private IChannelFactory<TChannel> InnerChannelFactory
{ get; set; } 

public MyChannelFactory(BindingContext context)
{
      this.InnerChannelFactory = context.BuildInnerChannelFactory<TChannel>();
} 

注：BindingContext 的两个最重要的方法就是BuildInnerChannelFactory和BuildInnerChannelListener。前者创建Inner channel factory后者创建Inner Channel listener。

熟悉了ChannelFactory的定义，大家很自然的想得到ChannelListner的定义（不过ChannelListner的成员比ChannelFactory 要多些）：

namespace Artech.ChannleStackExplore.Channels
{
    public class MyChannelListener<TChannel> : ChannelListenerBase<TChannel> where TChannel : class, IChannel
    {
        private IChannelListener<TChannel> InnerChannelListener
        { get; set; } 

        public MyChannelListener(BindingContext context)
        {
            this.InnerChannelListener = context.BuildInnerChannelListener<TChannel>();
        } 

        protected override TChannel OnAcceptChannel(TimeSpan timeout)
        {
            Console.WriteLine("MyChannelListener<TChannel>.OnAcceptChannel()");
            TChannel innerChannel = this.InnerChannelListener.AcceptChannel(timeout);
            return new MyReplyChannel(this, innerChannel as IReplyChannel) as TChannel;
        } 

        protected override IAsyncResult OnBeginAcceptChannel(TimeSpan timeout, AsyncCallback callback, object state)
        {
            Console.WriteLine("MyChannelListener<TChannel>.OnBeginAcceptChannel()");
           return this.InnerChannelListener.BeginAcceptChannel(timeout, callback, state);
        } 

        protected override TChannel OnEndAcceptChannel(IAsyncResult result)
        {
            Console.WriteLine("MyChannelListener<TChannel>.OnEndAcceptChannel()");
            TChannel innerChannel = this.InnerChannelListener.EndAcceptChannel(result);
            return new MyReplyChannel(this, innerChannel as IReplyChannel) as TChannel;
        } 

        protected override IAsyncResult OnBeginWaitForChannel(TimeSpan timeout, AsyncCallback callback, object state)
        {
            Console.WriteLine("MyChannelListener<TChannel>.OnBeginWaitForChannel()");
            return this.InnerChannelListener.BeginWaitForChannel(timeout, callback, state);
        } 

        protected override bool OnEndWaitForChannel(IAsyncResult result)
        {
            Console.WriteLine("MyChannelListener<TChannel>.OnEndWaitForChannel()");
            return this.InnerChannelListener.EndWaitForChannel(result);
        } 

        protected override bool OnWaitForChannel(TimeSpan timeout)
        {
            Console.WriteLine("MyChannelListener<TChannel>.OnWaitForChannel()");
            return this.InnerChannelListener.WaitForChannel(timeout);
        } 

        public override Uri Uri
        {
            get 
            {
                Console.WriteLine("MyChannelListener<TChannel>.Uri");
                return this.InnerChannelListener.Uri;
            } 

        } 

        protected override void OnAbort()
        {
            Console.WriteLine("MyChannelListener<TChannel>.OnAbort()");
            this.InnerChannelListener.Abort();
        } 

        protected override IAsyncResult OnBeginClose(TimeSpan timeout, AsyncCallback callback, object state)
        {
            Console.WriteLine("MyChannelListener<TChannel>.OnBeginClose()");
            return this.InnerChannelListener.BeginClose(timeout, callback, state);
        } 

        protected override IAsyncResult OnBeginOpen(TimeSpan timeout, AsyncCallback callback, object state)
        {
            Console.WriteLine("MyChannelListener<TChannel>.OnBeginOpen()");
            return this.InnerChannelListener.BeginOpen(timeout, callback, state);
        } 

        protected override void OnClose(TimeSpan timeout)
        {
            Console.WriteLine("MyChannelListener<TChannel>.OnClose()");
            this.InnerChannelListener.Close(timeout);
        } 

        protected override void OnEndClose(IAsyncResult result)
        {
            Console.WriteLine("MyChannelListener<TChannel>.OnEndClose()");
            this.InnerChannelListener.EndClose(result);
        } 

        protected override void OnEndOpen(IAsyncResult result)
        {
            Console.WriteLine("MyChannelListener<TChannel>.OnEndOpen()");
            this.InnerChannelListener.EndOpen(result);
        } 

        protected override void OnOpen(TimeSpan timeout)
        {
            Console.WriteLine("MyChannelListener<TChannel>.OnOpen()");
            this.InnerChannelListener.Open(timeout);
        }
    }
} 

5. 创建Custom Binding Element

我们知道Binding是Service mode layer进入Channel layer的中介，而Binding由一系列的Binding element组成。我们上面创建的Channel factory和Channel listener需要最终通过对应的BindingElement应用到Binding中才能最终发挥作用。我们就来创建这个BindingElement：MyBindingElement。

namespace Artech.ChannleStackExplore.Channels
{
  public class MyBindingElement:BindingElement
    {
        public override BindingElement Clone()
        {
            return new MyBindingElement();
        } 

        public override T GetProperty<T>(BindingContext context)
        {
            return context.GetInnerProperty<T>();
        } 

        public override IChannelFactory<TChannel> BuildChannelFactory<TChannel>(BindingContext context)
        {
            Console.WriteLine("MyBindingElement.BuildChannelFactory()");
            return new MyChannelFactory<TChannel>(context) as IChannelFactory<TChannel>;
        } 

        public override IChannelListener<TChannel> BuildChannelListener<TChannel>(BindingContext context)
        {
            Console.WriteLine("MyBindingElement.BuildChannelListener()");
            return new MyChannelListener<TChannel>(context) as IChannelListener<TChannel>;
        }
    }
} 

够简单吧，直接调用MyChannelFactory和MyChannelListener的构造函数就可以了。

6. 创建Custom Binding

我们进入了最后的阶段，创建一个Custom Binding。MyBinding继承Binding class。 在CreateBindingElements方法中将我们的Binding element（MyBindingElement），连同其他必须的Binding element添加到BindingElementCollection 中。

namespace Artech.ChannleStackExplore.Channels
{
    public class MyBinding:Binding
    {
        public override BindingElementCollection CreateBindingElements()
        {
            BindingElementCollection elemens = new BindingElementCollection();
            elemens.Add(new TextMessageEncodingBindingElement());
            elemens.Add(new MyBindingElement());
            elemens.Add(new HttpTransportBindingElement());
            return elemens.Clone();
        } 

        public override string Scheme
        {
            get
            {
                return "http";
            }
        }
    }
} 

注：对BindElement的组装可以通过configuration来实现。

7. 使用Custom Binding

我们上面所做的一切都汇集到我们的Custom binding：MyBinding。既然我们为之写了那么多代码，我们一定要通过某种方式测试一下它时候具有我们需要的功能。我们通过MyBinding创建一个Messaging via Binding的应用。不熟悉的朋友可以转到上一篇去熟悉一下。

Server端的代码：

namespace Server
{
    class Program
    {
        static void Main(string[] args)
        {
            MyBinding binding = new MyBinding();
            IChannelListener<IReplyChannel> channelListener= binding.BuildChannelListener<IReplyChannel>(new Uri("http://127.0.0.1:8888/messagingviabinding"));
            channelListener.Open();

            while (true)
            {
                IReplyChannel channel= channelListener.AcceptChannel(TimeSpan.MaxValue);
                channel.Open();
                RequestContext context = channel.ReceiveRequest(TimeSpan.MaxValue);

                Console.WriteLine("Receive a request message:/n{0}", context.RequestMessage);
                Message replyMessage = Message.CreateMessage(MessageVersion.Soap12WSAddressing10, "http://artech.messagingviabinding", "This is a mannualy created reply message for the purpose of testing");
                context.Reply(replyMessage);
                channel.Close();
            }
        }
    }
}

Client端的代码：

 

namespace Client
{
    class Program
    {
        static void Main(string[] args)
        {
            MyBinding binding = new MyBinding();
            IChannelFactory<IRequestChannel> channelFactory = binding.BuildChannelFactory<IRequestChannel>();
            channelFactory.Open();

            IRequestChannel channel = channelFactory.CreateChannel(new EndpointAddress("http://127.0.0.1:8888/messagingviabinding"));
            channel.Open();

            Message requestMessage = Message.CreateMessage(MessageVersion.Soap12WSAddressing10, "http://artech.messagingviabinding", "This is a mannualy created reply message for the purpose of testing");
            Message replyMessage = channel.Request(requestMessage);
            Console.WriteLine("Receive a reply message:/n{0}", replyMessage);
            channel.Close();
            channelFactory.Close();
            Console.Read();
        } 

    }
} 

运行的结果将会是这样:

Server:

Client:

通过上面的输出结果，你很直观的了解到了整个程序执行过程中，我们的定义在Channel，Channel factory，Channel listener和Binding element的方法是如何被依次执行的。

 

 

WCF后续之旅：
[原创]WCF后续之旅(1): WCF是如何通过Binding进行通信的
[原创]WCF后续之旅(2): 如何对Channel Layer进行扩展——创建自定义Channel
[原创]WCF后续之旅(3): WCF Service Mode Layer 的中枢—Dispatcher
[原创]WCF后续之旅(4)：WCF Extension Point 概览
[原创]WCF后续之旅(5): 通过WCF Extension实现Localization
[原创]WCF后续之旅(6): 通过WCF Extension实现Context信息的传递
[原创]WCF后续之旅(7)：通过WCF Extension实现和Enterprise Library Unity Container的集成
[原创]WCF后续之旅(8)：通过WCF Extension 实现与MS Enterprise Library Policy Injection Application Block 的集成
[原创]WCF后续之旅(9)：通过WCF的双向通信实现Session管理[Part I]
[原创]WCF后续之旅(9): 通过WCF双向通信实现Session管理[Part II]
[原创]WCF后续之旅(10): 通过WCF Extension实现以对象池的方式创建Service Instance

我的WCF之旅：
[原创]我的WCF之旅（1）：创建一个简单的WCF程序
[原创]我的WCF之旅（2）：Endpoint Overview
[原创]我的WCF之旅（3）：在WCF中实现双向通信（Bi-directional Communication）
[原创]我的WCF之旅（4）：WCF中的序列化（Serialization）- Part I
[原创]我的WCF之旅（4）：WCF中的序列化（Serialization）- Part II
[原创]我的WCF之旅（5）：Service Contract中的重载（Overloading）
[原创]我的WCF之旅（6）：在Winform Application中调用Duplex Service出现TimeoutException的原因和解决方案
[原创]我的WCF之旅（7）：面向服务架构（SOA）和面向对象编程（OOP）的结合——如何实现Service Contract的继承
[原创]我的WCF之旅（8）：WCF中的Session和Instancing Management
[原创]我的WCF之旅（9）：如何在WCF中使用tcpTrace来进行Soap Trace
[原创]我的WCF之旅（10）： 如何在WCF进行Exception Handling
[原创]我的WCF之旅（11）：再谈WCF的双向通讯-基于Http的双向通讯 V.S. 基于TCP的双向通讯
[原创]我的WCF之旅（12）：使用MSMQ进行Reliable Messaging
[原创]我的WCF之旅（13）：创建基于MSMQ的Responsive Service