WCF基础:绑定(二)

在WCF的绑定体系中，经常会碰到ICommunicationObject接口，无论是IChannel接口还是IChannelListener/IChannelFactory接口都继承了ICommunicationObject接口;可见ICommunicationObject接口在Bing体系中作用很重要；

ICommunicationObject

ICommunicationObject接口是通信对象状态装换的接口；

    public interface ICommunicationObject
    {
        event EventHandler Closed;
        event EventHandler Closing;
        event EventHandler Faulted;
        event EventHandler Opened;
        event EventHandler Opening;
        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);
        CommunicationState State {  get; }
    }

public enum CommunicationState
{
Closed = 4,
Closing = 3,
Created = 0,
Faulted = 5,
Opened = 2,
Opening = 1
}

ICommunicationObject接口中的CommunicationState 枚举代表了通信对象的五种状态，而且在ICommunicationObject接口中提供了5个事件来对应通信对象的状态装换;比如在Open()方法中首先调用Opening事件，在方法结束之前调用Opened 事件;

CommunicationObject

在WCF中抽象类CommunicationObject继承了 ICommunicationObject接口，CommunicationObject类的目的是为系统中所有面向通信的对象（包括通道、侦听器以及通道和侦听器工厂）公用的基本状态机提供通用的基实现。在抽象类中定义了一些通信对象在进行状态转换中的处理方法，通过这些抽象方法可以扩展相关的实现，比如ICommunicationObject接口的方法；

public abstract class CommunicationObject : ICommunicationObject
{
     public void Open()
     {
       this.Open(this.DefaultOpenTimeout);
     }

     public void Open(TimeSpan timeout)
     {
           using (ServiceModelActivity activity = (DiagnosticUtility.ShouldUseActivity && this.TraceOpenAndClose) ? ServiceModelActivity.CreateBoundedActivity() : null)
       {
           if (DiagnosticUtility.ShouldUseActivity)
           {
              ServiceModelActivity.Start(activity, this.OpenActivityName, this.OpenActivityType);
           }
           lock (this.ThisLock)
           {
              this.ThrowIfDisposedOrImmutable();
              this.state = CommunicationState.Opening;
            }
            bool flag = true;
            try
            {
               System.Runtime.TimeoutHelper helper = new System.Runtime.TimeoutHelper(timeout);
               this.OnOpening();
               if (!this.onOpeningCalled)
                {
                    throw TraceUtility.ThrowHelperError(this.CreateBaseClassMethodNotCalledException("OnOpening"), Guid.Empty, this);
                }
                this.OnOpen(helper.RemainingTime());
                this.OnOpened();
                if (!this.onOpenedCalled)
                {
                    throw TraceUtility.ThrowHelperError(this.CreateBaseClassMethodNotCalledException("OnOpened"), Guid.Empty, this);
                }
                flag = false;
                }
                finally
                {
                 if (flag)
                 {
                    if (DiagnosticUtility.ShouldTraceWarning)
                    {
                        TraceUtility.TraceEvent(TraceEventType.Warning, 0x80005, System.ServiceModel.SR.GetString("TraceCodeCommunicationObjectOpenFailed", new object[] { this.GetCommunicationObjectType().ToString() }), this);
                     }
                   this.Fault();
                  }
               }
            }
        }
   protected abstract void OnOpen(TimeSpan timeout);
}

在CommunicationObject类执行Open方法，参数TimeSpan timeout为方法调用超时的时间；

1.通过 this.state = CommunicationState.Opening 将通信对象的状态设置为正在打开的状态;

2.调用 this.OnOpening()方法其实方法的内部就是调用ICommunicationObject接口的 EventHandler Opening 事件处理函数;

3.然后执行 this.OnOpen(helper.RemainingTime())方法这个方法时抽象方法，需要在子类中进行扩展这个方法;

4.当1.2.3都执行完毕后，这说明通信对象已经打开，然后调用this.OnOpened()方法，在这个方法执行EventHandler Opened事件处理函数，并将通信对象的状态设置为Opened状态;

5.如果1.2.3.4的过程中有报错，则会将通信对象的状态设置为Fault状态;

对于CommunicationObject类中其他的状态变更比如Close，Abort等类似方法都是相同的流程；