WCF，IDispatchOperationSelector：当操作不存在时返回自定义 FaultException

Question

在我的 WCF 服务中，我正在使用这样的自定义 DispatchOperationSelector：

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;
    }

    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
        {
            //Here : operation not found !
            //this doesn't work : throw new FaultException<ValidationException>(new ValidationException()); 

            return null;
        }
    }

    #endregion
}

如果请求的操作不存在，我想返回自定义 FaultException（而不是返回 null 并在我的代码中出现 ArgumentNullException 异常）。

我该怎么做？

编辑：

结果为“throw new FaultException(new ValidationException());”说明：

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/" xmlns:u="http://test.com/utility-1.0.xsd">
   <s:Header>
      <o:Security s:mustUnderstand="1" xmlns:o="http://test.com/secext-1.0.xsd">
         <u:Timestamp u:Id="_0">
            <u:Created>2015-09-15T07:48:23.199Z</u:Created>
            <u:Expires>2015-09-15T07:53:23.199Z</u:Expires>
         </u:Timestamp>
      </o:Security>
   </s:Header>
   <s:Body>
      <s:Fault>
         <faultcode xmlns:a="http://schemas.microsoft.com/net/2005/12/windowscommunicationfoundation/dispatcher">a:InternalServiceFault</faultcode>
         <faultstring xml:lang="fr-FR">The creator of this fault did not specify a Reason.</faultstring>
         <detail>
            <ExceptionDetail xmlns="http://schemas.datacontract.org/2004/07/System.ServiceModel" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
               <HelpLink i:nil="true"/>
               <InnerException i:nil="true"/>
               <Message>The creator of this fault did not specify a Reason.</Message>
               <StackTrace>at Demo.Demo11WcfService.DispatchByBodyElementOperationSelector.SelectOperation(Message&amp; message) in d:\Activite\TRACA\DEV\Main\DemoSolution2\DemoSolution2\Demo.Demo11WcfService\DispatchByBodyOperationSelector.cs:line 47
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.CustomDemuxer.GetOperation(Message&amp; request)
   at System.ServiceModel.Dispatcher.ChannelHandler.DispatchAndReleasePump(RequestContext request, Boolean cleanThread, OperationContext currentOperationContext)</StackTrace>
               <Type>System.ServiceModel.FaultException`1[Demo.DomainModel.Demo11.ValidationException]</Type>
            </ExceptionDetail>
         </detail>
      </s:Fault>
   </s:Body>
</s:Envelope>

预期结果：

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/" xmlns:u="http://test.com/utility-1.0.xsd">
   <s:Header>
      <o:Security s:mustUnderstand="1" xmlns:o="http://test.com/secext-1.0.xsd">
         <u:Timestamp u:Id="_0">
            <u:Created>2015-09-15T07:49:55.610Z</u:Created>
            <u:Expires>2015-09-15T07:54:55.610Z</u:Expires>
         </u:Timestamp>
      </o:Security>
   </s:Header>
   <s:Body>
      <s:Fault>
         <faultcode>s:Client</faultcode>
         <faultstring xml:lang="fr-FR">The creator of this fault did not specify a Reason.</faultstring>
         <detail>
            <ValidationException xmlns="http://schemas.datacontract.org/2004/07/Demo.DomainModel.Demo11" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
               <reasonField i:nil="true"/>
            </ValidationException>
         </detail>
      </s:Fault>
   </s:Body>
</s:Envelope>

Answer 1

由于我显然无法发表评论，我将把它留在这里（如果不合适，请随时删除答案）：

您是否尝试过只抛出自定义 FaultException 而不是返回 null？