Question

我有一个没有互操作性要求的自定义Intranet应用程序。我们以双工模式编程构造NetTcp通道以传递消息。我们想要改变消息编码，但却无法弄清楚如何实现这一点。

我们采取的方法（失败）是将NetTcpBinding扩展为一个名为LeanTcpBinding的新类，如下所示：


internal class LeanTcpBinding : NetTcpBinding
{
    private static readonly ILog _log =
        LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

    public override BindingElementCollection CreateBindingElements()
    {
        BindingElementCollection bindingElementCollection = base.CreateBindingElements();
        BindingElement encodingElement = bindingElementCollection.FirstOrDefault(
            bindingElement => bindingElement is BinaryMessageEncodingBindingElement);
        if (encodingElement != null)
        {
            int index = bindingElementCollection.IndexOf(encodingElement);
            bindingElementCollection.RemoveAt(index);
            bindingElementCollection.Insert(index, new LeanBinaryMessageEncodingBindingElement());
        }
        else
        {
            _log.Warn("Encoding not found");
        }

        return bindingElementCollection;
    }
}

显然，我们正在尝试用我们自己的替换默认的BinaryMessageEncodingBindingElement。为了开始使用，LeanBinaryMessageEncodingBindingElement是BinaryMessageEncodingBindingElement的扩展，如下所示：


 internal class LeanBinaryMessageEncodingBindingElement : MessageEncodingBindingElement
 {
        private readonly BinaryMessageEncodingBindingElement _bindingElement;

        /// 
        /// Initializes a new instance of the  class.
        /// 
        public LeanBinaryMessageEncodingBindingElement()
        {
            _bindingElement = new BinaryMessageEncodingBindingElement();
        }

        /// 
        /// Initializes a new instance of the  class.
        /// 
        /// The binding element.
        public LeanBinaryMessageEncodingBindingElement(BinaryMessageEncodingBindingElement bindingElement)
        {
            _bindingElement = bindingElement;
        }

        /// 
        /// Initializes a new instance of the  class.
        /// 
        /// The element to be cloned.
        /// The binding element.
        public LeanBinaryMessageEncodingBindingElement(MessageEncodingBindingElement elementToBeCloned, BinaryMessageEncodingBindingElement bindingElement)
            : base(elementToBeCloned)
        {
            _bindingElement = bindingElement;
        }

        /// 
        /// When overridden in a derived class, returns a copy of the binding element object.
        /// 
        /// 
        /// A  object that is a deep clone of the original.
        /// 
        public override BindingElement Clone()
        {
            return new LeanBinaryMessageEncodingBindingElement(
                (BinaryMessageEncodingBindingElement)_bindingElement.Clone());
        }

        /// 
        /// When overridden in a derived class, creates a factory for producing message encoders.
        /// 
        /// 
        /// The  used to produce message encoders.
        /// 
        public override MessageEncoderFactory CreateMessageEncoderFactory()
        {
            return new LeanBinaryMessageEncoderFactory(_bindingElement.CreateMessageEncoderFactory());
        }

        /// 
        /// When overridden in a derived class, gets or sets the message version that can be handled by the message encoders produced by the message encoder factory.
        /// 
        /// 
        /// The  used by the encoders produced by the message encoder factory.
        /// 
        public override MessageVersion MessageVersion
        {
            get { return _bindingElement.MessageVersion; }
            set { _bindingElement.MessageVersion = value; }
        }
 }

当我尝试使用绑定时，它完全按照我认为它应该做的...它取代了BinaryMessageEncodingBindingElement。但是，即使通过通道交换消息，我也永远不会调用LeanBinaryMessageEncodingBindingElement.CreateMessageEncoderFactory（）。

有人对如何正确地做这件事有任何建议吗？

Answer 1

肯尼·沃尔夫澄清了遗漏的内容，并在下面的博客文章中进行了记录。

http://kennyw.com/?p=170

对于不耐烦的人，问题是默认情况下MessageEncoderBindingElement不会将自身添加到上下文的绑定参数中。结果，当传输后来找到MessageEncoderBindingElement时，它找不到我（或你）创建的那个，并且我在原始帖子中注意到了无声失败。

不幸的是，您必须按如下方式覆盖所有CanBuildXXX和BuildXXX方法，以确保将绑定元素添加到上下文的绑定参数中。


        public override bool CanBuildChannelFactory(BindingContext context)
        {
            if (context == null) {
                throw new ArgumentNullException("context");
            }

            context.BindingParameters.Add(this);
            return context.CanBuildInnerChannelFactory();
        }

        public override bool CanBuildChannelListener(BindingContext context)
        {
            if (context == null) {
                throw new ArgumentNullException("context");
            }

            context.BindingParameters.Add(this);
            return context.CanBuildInnerChannelListener();
        }

        public override IChannelFactory BuildChannelFactory(BindingContext context)
        {
            if (context == null) {
                throw new ArgumentNullException("context");
            }

            context.BindingParameters.Add(this);
            return context.BuildInnerChannelFactory();
        }

        public override IChannelListener BuildChannelListener(BindingContext context)
        {
            if (context == null) {
                throw new ArgumentNullException("context");
            }

            context.BindingParameters.Add(this);
            return context.BuildInnerChannelListener();
        }

Answer 2

您是否尝试过使用NetTcpBinding配置创建CustomBinding？像这样：

NetTcpBinding binding = new NetTcpBinding(); // get binding from somewhere
var elements = binding.CreateBindingElements();
BindingElementCollection newElements = new BindingElementCollection();
foreach ( var e in elements ) {
   if ( e is MessageEncodingBindingElement ) {
      newElements.Add(new MyMessageEncodingBindingElement());
   } else {
      newElements.Add(e);
   }
}
CustomBinding cb = new CustomBinding(newElements);

如何以编程方式更改NetTcp的WCF消息编码？

2 个答案: