c# - 我已经实现了 AfterReceiveRequest 方法(来自 IDispatchMessageInspector)，并且想要验证请求是否有效？

Question

在我的客户端中，在调用服务之前，我在发送到 wcf 服务之前向请求添加了一个 token (guid)。

AfterReceiveRequest(ref System.ServiceModel.Channels.Message request, System.ServiceModel.IClientChannel channel, System.ServiceModel.InstanceContext instanceContext)

在此方法中，我想验证请求 header 是否具有在客户端中添加的 token (guid)。所以我在这里使用了这部分代码:

Guid securityTokenId = request.Headers.GetHeader<Guid>("Token", "System");

如果在任何情况下在 header 中找不到此“ token ”，我的 securityTokenId 是否会返回 Guid.Empty？或者它返回什么？

Answer 1

如果没有具有该名称/命名空间的 header ，您将在调用 GetHeader 时收到异常 (MessageHeaderException)。如果不想处理异常，可以先查看这样的 header 是否存在(使用 FindHeader 方法)，然后如果返回非负值，则获取对应的 header。

public class StackOverflow_8854137
{
    [ServiceContract]
    public interface ITest
    {
        [OperationContract]
        string Echo(string text);
    }
    public class Service : ITest
    {
        public string Echo(string text)
        {
            return text;
        }
    }
    class MyBehavior : IEndpointBehavior, IDispatchMessageInspector
    {
        public void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters)
        {
        }

        public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime)
        {
        }

        public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
        {
            endpointDispatcher.DispatchRuntime.MessageInspectors.Add(this);
        }

        public void Validate(ServiceEndpoint endpoint)
        {
        }

        public object AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext)
        {
            try
            {
                Guid tokenId = request.Headers.GetHeader<Guid>("Token", "System");
                Console.WriteLine("Token: {0}", tokenId);
            }
            catch (Exception e)
            {
                Console.WriteLine("{0}: {1}", e.GetType().FullName, e.Message);
            }

            return null;
        }

        public void BeforeSendReply(ref Message reply, object correlationState)
        {
        }
    }
    public static void Test()
    {
        string baseAddress = "http://" + Environment.MachineName + ":8000/Service";
        ServiceHost host = new ServiceHost(typeof(Service), new Uri(baseAddress));
        ServiceEndpoint endpoint = host.AddServiceEndpoint(typeof(ITest), new BasicHttpBinding(), "");
        endpoint.Behaviors.Add(new MyBehavior());
        host.Open();
        Console.WriteLine("Host opened");

        ChannelFactory<ITest> factory = new ChannelFactory<ITest>(new BasicHttpBinding(), new EndpointAddress(baseAddress));
        ITest proxy = factory.CreateChannel();
        Console.WriteLine(proxy.Echo("No token"));

        using (new OperationContextScope((IContextChannel)proxy))
        {
            OperationContext.Current.OutgoingMessageHeaders.Add(MessageHeader.CreateHeader("Token", "System", Guid.NewGuid()));
            Console.WriteLine(proxy.Echo("With token"));
        }

        ((IClientChannel)proxy).Close();
        factory.Close();

        Console.Write("Press ENTER to close the host");
        Console.ReadLine();
        host.Close();
    }
}