将 XElement 类型作为 WCF 服务中的对象返回时出错

Question

这是我的操作合同：

[ServiceContract]
public interface IService
{

    [OperationContract]
    object Move();

}

这是操作合同的实现。我想将 XElement 作为对象返回，让客户端将对象转换回 XElement

public object Move()
    {
        object _x;

            var xmlTree1 = new XElement("Root",
                                        new XElement("Child", 1),
                                        new XElement("Child", 2),
                                        new XElement("Child", 3),
                                        new XElement("Child", 4),
                                        new XElement("Child", 5),
                                        new XElement("Child", 6)
                );

            var xmlTree2 = new XElement("Root",
                                        from el in xmlTree1.Elements()
                                        where ((int) el >= 3 && (int) el <= 5)
                                        select el


                );

            _x = xmlTree2;

            return _x;

    }

这是客户端代码：

XElement _xmlelem;

ServiceClient sc = new ServiceClient();

_xmlelem = (XElement)sc.Move();

下面是错误消息的堆栈跟踪：

Server stack trace: 
   at System.ServiceModel.Channels.HttpChannelUtilities.ProcessGetResponseWebException(WebException webException, HttpWebRequest request, HttpAbortReason abortReason)
   at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout)
   at System.ServiceModel.Channels.RequestChannel.Request(Message message, TimeSpan timeout)
   at System.ServiceModel.Channels.ClientReliableChannelBinder`1.RequestClientReliableChannelBinder`1.OnRequest(TRequestChannel channel, Message message, TimeSpan timeout, MaskingMode maskingMode)
   at System.ServiceModel.Channels.ClientReliableChannelBinder`1.Request(Message message, TimeSpan timeout, MaskingMode maskingMode)
   at System.ServiceModel.Channels.ClientReliableChannelBinder`1.Request(Message message, TimeSpan timeout)
   at System.ServiceModel.Security.SecuritySessionClientSettings`1.SecurityRequestSessionChannel.Request(Message message, TimeSpan timeout)
   at System.ServiceModel.Dispatcher.RequestChannelBinder.Request(Message message, TimeSpan timeout)
   at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
   at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs)
   at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
   at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)

Exception rethrown at [0]: 
   at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
   at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
   at ConsoleApplication1.ServiceReference1.IService.Move()
   at ConsoleApplication1.ServiceReference1.ServiceClient.Move() in C:\Delete\ConsoleApplication1\Service References\ServiceReference1\Reference.cs:line 128
   at ConsoleApplication1.Program.Main(String[] args) in C:\Delete\ConsoleApplication1\Program.cs:line 20
   at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
   at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
   at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

Answer 1

您要求 WCF 服务将 .NET 类型（在您的情况下为 XElement）反序列化到发出请求的客户端，然后让客户端将 .NET 对象类型返回值转换为 XElement 类型。 WCF 不支持这种反序列化，除非您通过 使用 NetDataContractSerializer 而不是标准 DataContractSerializer。

使用 NetDataContractSerializer 所以一般来说这不是一个好的做法。我相信您最好直接返回 XML。答案在此问题展示了如何处理数据契约中的XML。