扩展WCF行为，自定义消息头，实现客户端标识的传递

一 需求

服务端每次为客户端提供服务调用时，需要知道客户端的标识。客户端如何在每次调用时传递此标识？

二 解决

客户端

static void HandleFactory(ChannelFactory factory)
{
    Debug.Assert(factory != null && factory.Credentials != null);
    factory.Endpoint.Behaviors.Add(new ClientMessageInspector{ HeaderValue=new []{"哈啰"} });
}

private class ClientMessageInspector : System.ServiceModel.Dispatcher.IClientMessageInspector, System.ServiceModel.Description.IEndpointBehavior
{
    public string HeaderValue { get; set; }

    #region Implementation for IClientMessageInspector
    public void AfterReceiveReply(ref System.ServiceModel.Channels.Message reply, object correlationState) { }

    public object BeforeSendRequest(ref System.ServiceModel.Channels.Message request, System.ServiceModel.IClientChannel channel)
    {
	request.Headers.Add(System.ServiceModel.Channels.MessageHeader.CreateHeader("id", "client", HeaderValue));
	return null;
    }
    #endregion

    #region Implementation for IEndpointBehavior
    //==================================
    public void AddBindingParameters(System.ServiceModel.Description.ServiceEndpoint serviceEndpoint, System.ServiceModel.Channels.BindingParameterCollection bindingParameters) { }

    public void ApplyClientBehavior(System.ServiceModel.Description.ServiceEndpoint serviceEndpoint, ClientRuntime behavior)
    {
	//此处为Extension附加到ClientRuntime。
	behavior.MessageInspectors.Add(this);
    }

    public void ApplyDispatchBehavior(System.ServiceModel.Description.ServiceEndpoint serviceEndpoint, EndpointDispatcher endpointDispatcher)
    {
	//如果是扩展服务器端的MessageInspector，则要附加到EndpointDispacther上了。
	//endpointDispatcher.DispatchRuntime.MessageInspectors.Add(this);
    }

    public void Validate(System.ServiceModel.Description.ServiceEndpoint serviceEndpoint) { }
    #endregion
}

服务端

var clientId=OperationContext.Current.IncomingMessageHeaders.GetHeader<string>("id","client");

三 参考

Writing a WCF Message Inspector

利用定制行为扩展WCF之-利用MessageInsepctor behaviourExtension扩展WCF行为（自定义消息头）