错误“此消息无法支持该操作，因为它已被读取”答案

【问题标题】：Error "This message cannot support the operation because it has been read"错误“此消息无法支持该操作，因为它已被读取”
【发布时间】：2012-06-17 20:38:41
【问题描述】：

我遇到了以下线程中列出的相同问题。

WSDL first WCF server where client does not send SOAPAction

我执行了同一线程中列出的步骤（如下所示）

1) 下载 Microsoft WCF 示例。从 WF_WCF_Samples\WCF\Extensibility\Interop\RouteByBody\CS\service 将以下文件添加到您的项目中

DispatchByBodyOperationSelector.cs

DispatchByBodyBehaviorAttribute.cs

2) 将以下属性添加到您的界面（在您的 ServiceContract 旁边）

XmlSerializerFormat

DispatchByBodyBehavior

3) 将以下内容添加到您的服务接口中

[OperationContract(Action = "")]

public void DoNothing()
{
}

4) 对于我的服务，WrapperName 和 Wrappernamespace 对于所有消息都是空的。我必须进入 DispatchByBodyBehaviorAttribute 并编辑 ApplyDispatchBehavior() 以添加以下行来检查：

 if (qname.IsEmpty) {
     qname = new XmlQualifiedName(operationDescription.Messages[0].Body.Parts[0].Name, operationDescription.Messages[0].Body.Parts[0].Namespace);
 }

现在，我收到一条错误消息“此消息无法支持该操作，因为它已被读取”。我打开了跟踪并捕获了堆栈跟踪（如下）。如果有人对如何解决此问题有任何想法，如果您能发布一些 cmets，我将不胜感激。感谢您的帮助！

at System.ServiceModel.Channels.Message.GetReaderAtBodyContents()
at System.ServiceModel.Dispatcher.OperationFormatter.DeserializeBodyContents(Message message, Object[] parameters, Boolean isRequest)
at System.ServiceModel.Dispatcher.OperationFormatter.DeserializeRequest(Message message, Object[] parameters)
at System.ServiceModel.Dispatcher.DispatchOperationRuntime.DeserializeInputs(MessageRpc&amp; rpc)
at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc&amp; rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc&amp; rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage41(MessageRpc&amp; rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage4(MessageRpc&amp; rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage31(MessageRpc&amp; rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage3(MessageRpc&amp; rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage2(MessageRpc&amp; rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage11(MessageRpc&amp; rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage1(MessageRpc&amp; rpc)
at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)
at System.ServiceModel.Dispatcher.ChannelHandler.DispatchAndReleasePump(RequestContext request, Boolean cleanThread, OperationContext currentOperationContext)
at System.ServiceModel.Dispatcher.ChannelHandler.HandleRequest(RequestContext request, OperationContext currentOperationContext)
at System.ServiceModel.Dispatcher.ChannelHandler.AsyncMessagePump(IAsyncResult result)
at System.ServiceModel.Dispatcher.ChannelHandler.OnAsyncReceiveComplete(IAsyncResult result)
at System.Runtime.Fx.AsyncThunk.UnhandledExceptionFrame(IAsyncResult result)
at System.Runtime.AsyncResult.Complete(Boolean completedSynchronously)
at System.Runtime.InputQueue`1.AsyncQueueReader.Set(Item item)
at System.Runtime.InputQueue`1.EnqueueAndDispatch(Item item, Boolean canDispatchOnThisThread)
at System.Runtime.InputQueue`1.EnqueueAndDispatch(T item, Action dequeuedCallback, Boolean canDispatchOnThisThread)
at System.ServiceModel.Channels.SingletonChannelAcceptor`3.Enqueue(QueueItemType item, Action dequeuedCallback, Boolean canDispatchOnThisThread)
at System.ServiceModel.Channels.HttpChannelListener.HttpContextReceived(HttpRequestContext context, Action callback)
at System.ServiceModel.Channels.SharedHttpTransportManager.OnGetContextCore(IAsyncResult result)
at System.ServiceModel.Channels.SharedHttpTransportManager.OnGetContext(IAsyncResult result)
at System.Runtime.Fx.AsyncThunk.UnhandledExceptionFrame(IAsyncResult result)
at System.Net.LazyAsyncResult.Complete(IntPtr userToken)
at System.Net.LazyAsyncResult.ProtectedInvokeCallback(Object result, IntPtr userToken)
at System.Net.ListenerAsyncResult.WaitCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* nativeOverlapped)
at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP)
</StackTrace>


class DispatchByBodyElementOperationSelector : IDispatchOperationSelector
{
    Dictionary<XmlQualifiedName, string> dispatchDictionary;

    public DispatchByBodyElementOperationSelector(Dictionary<XmlQualifiedName, string> dispatchDictionary)
    {
        this.dispatchDictionary = dispatchDictionary;            
    }

    #region IDispatchOperationSelector Members

    private Message CreateMessageCopy(Message message, XmlDictionaryReader body)
    {
        //Message copy = Message.CreateMessage(message.Version, message.Headers.Action, body);
        //copy.Headers.CopyHeaderFrom(message, 0);
        //copy.Properties.CopyProperties(message.Properties);
        //return copy;    

        MessageBuffer buffer = message.CreateBufferedCopy(Int32.MaxValue);
        Message copy = buffer.CreateMessage();
        buffer.Close();
        copy.Headers.CopyHeaderFrom(message, 0);
        copy.Properties.CopyProperties(message.Properties);

        return copy;
    }

    public string SelectOperation(ref System.ServiceModel.Channels.Message message)
    {
        XmlDictionaryReader bodyReader = message.GetReaderAtBodyContents();

        XmlQualifiedName lookupQName = new XmlQualifiedName(bodyReader.LocalName, bodyReader.NamespaceURI);
        message = CreateMessageCopy(message,bodyReader);
        if (dispatchDictionary.ContainsKey(lookupQName))
        {
            return dispatchDictionary[lookupQName];
        }
        else
        {
            return null;
        }
    }

    #endregion
}

[AttributeUsage(AttributeTargets.Class|AttributeTargets.Interface)]
sealed class DispatchByBodyBehaviorAttribute : Attribute, IContractBehavior
{
    #region IContractBehavior Members

    public void AddBindingParameters(ContractDescription contractDescription, ServiceEndpoint endpoint, System.ServiceModel.Channels.BindingParameterCollection bindingParameters)
    {
        // no binding parameters need to be set here
        return;
    }

    public void ApplyClientBehavior(ContractDescription contractDescription, ServiceEndpoint endpoint, System.ServiceModel.Dispatcher.ClientRuntime clientRuntime)
    {
        // this is a dispatch-side behavior which doesn't require
        // any action on the client
        return;
    }

    public void ApplyDispatchBehavior(ContractDescription contractDescription, ServiceEndpoint endpoint, System.ServiceModel.Dispatcher.DispatchRuntime dispatchRuntime)
    {
        // We iterate over the operation descriptions in the contract and
        // record the QName of the request body child element and corresponding operation name
        // to the dictionary to be used for dispatch 
        Dictionary<XmlQualifiedName,string> dispatchDictionary = new Dictionary<XmlQualifiedName,string>();
        foreach( OperationDescription operationDescription in contractDescription.Operations )
        {
            XmlQualifiedName qname =
                new XmlQualifiedName(operationDescription.Messages[0].Body.WrapperName, operationDescription.Messages[0].Body.WrapperNamespace);




            if (qname.IsEmpty)
            {
                qname = new XmlQualifiedName(operationDescription.Messages[0].Body.Parts[0].Name, operationDescription.Messages[0].Body.Parts[0].Namespace);
            }

            dispatchDictionary.Add(qname, operationDescription.Name);                
        }

        // Lastly, we create and assign and instance of our operation selector that
        // gets the dispatch dictionary we've just created.
        dispatchRuntime.OperationSelector = 
            new DispatchByBodyElementOperationSelector(dispatchDictionary);
    }

    public void Validate(ContractDescription contractDescription, ServiceEndpoint endpoint)
    {
        // 
    }

    #endregion
}

【问题讨论】：

标签： wcf wcf-binding

【解决方案1】：

你应该使用MessageBuffer.CreateMessage:

Message 实例的主体只能使用或写入一次。如果您希望多次使用 Message 实例，您应该使用MessageBuffer 类完全存储整个Message 实例到内存中。

http://msdn.microsoft.com/en-us/library/system.servicemodel.channels.messagebuffer.aspx

我当前项目的代码：

public void AfterReceiveReply(ref System.ServiceModel.Channels.Message reply, object correlationState)
{
    MessageBuffer buffer = reply.CreateBufferedCopy(Int32.MaxValue);
    reply = buffer.CreateMessage();
    Message m = buffer.CreateMessage();
    LogMessage(m, " Response => ");
}

为Message 参数添加ref 并返回新消息。

 private Message CreateMessageCopy(ref Message message, XmlDictionaryReader body)
{
...
   message = buffer.CreateMessage();

【讨论】：

感谢您发布代码。在我的场景中，我正在重用来自 WCF 示例下载的类。我尝试将 MessageBuffer 代码放在 CreateMessageCopy 方法中，如下所示，但它对我不起作用。
我已经编辑了我的原始问题并发布了我从 WCF 示例中重用的两个类。我注释掉了 CreateMessageCopy() 中的现有代码，并尝试使用 MessageBuffer 创建消息。当我运行我的客户端时，它失败了。 MessageBuffer 缓冲区 = message.CreateBufferedCopy(Int32.MaxValue);
看起来该消息在到达此行之前已被阅读。我不确定应该将 MessageBuffer 代码放在哪里。有任何想法吗？谢谢！
我按照您的建议尝试了 ref，但仍然出现相同的错误。我还尝试在 SelectOperation() 处放置一个断点，并注意到它在第一次到达 MessageBuffer buffer = message.CreateBufferedCopy(Int32.MaxValue) 行时触发了错误。我不知道为什么它说该消息已被阅读，即使它是第一次到达这一行。
您在此处阅读消息 copy.Headers.CopyHeaderFrom(message, 0); copy.Properties.CopyProperties(message.Properties);

【解决方案2】：

我也遇到了一个非常相似的问题，我也使用了 WCF Samples 中的代码（确切地说是 RouteByBody），并且能够以不同的方式解决它，所以我会在此处发布它以防对任何人有所帮助。

情况： 客户端应用程序（消费者）可以在Release中工作，但是，当附加调试器时，它总是会失败并出现错误“此消息无法支持该操作，因为它已被读取” em>。

经过大量跟踪和记录 WCF 消息后，唯一对我有用的解决方案竟然如此简单：

我的服务托管在 IIS 上，debug="true" 在 web.config 的 <compilation> 部分中。

将其更改为debug="false" 在服务上解决了我所有的问题。

【讨论】：

那么我们将如何调试呢？
这对我们有用。从进程中分离调试器允许消息通过。附加调试器将导致 InvalidOperationException “消息无法支持此操作，因为它已被读取”。此外，该错误似乎仅在 DispatchByBodyBehavior 用于服务时发生。

【解决方案3】：

如果您正在调试服务，Dmitry Harnitski 的回答不起作用（它会给您“此消息无法支持该操作，因为它已被复制。”错误。）

即使在调试模式下也可以：

XmlDictionaryReader GetReader(ref Message message)
{
    MessageBuffer buffer = message.CreateBufferedCopy(Int32.MaxValue);
    message = buffer.CreateMessage();
    newMessage = buffer.CreateMessage();
    XmlDictionaryReader rv = buffer.CreateMessage().GetReaderAtBodyContents();
    buffer.Close();
    return rv;
}

static System.ServiceModel.Channels.Message newMessage = null;
static System.ServiceModel.Channels.Message lastMessage = null;

public string SelectOperation(ref System.ServiceModel.Channels.Message message)
{
    try
    {
        if(message == lastMessage)
            message = newMessage;

        XmlDictionaryReader bodyReader = GetReader(ref message);

        lastMessage = message;

        XmlQualifiedName lookupQName = new XmlQualifiedName(bodyReader.LocalName, bodyReader.NamespaceURI);
        if (dispatchDictionary.ContainsKey(lookupQName))
        {
            return dispatchDictionary[lookupQName];
        }
        else
        {
            return null;
        }
    }
    catch(Exception ex)
    {
        throw ex;
    }
}

【讨论】：