通过WCF流​​式传输文件时出现ArgumentNullException

Question

我有一个WCF流式二进制文件。以下是合同的缩短版本。

[MessageContract()]
public class DocumentTransfer
{
    [MessageHeader(MustUnderstand = true)]
    public string Title { get; set; }

    [MessageHeader(MustUnderstand = true)]
    public string FileName { get; set; }

    [MessageBodyMember(Order = 1)]
    public System.IO.Stream Data;
}

一切正常但有些情况下只需要更新与文件关联的其他一些值，而不是文件本身。在这种情况下，客户端设置Data = null。然后无法解释/序列化Data属性并抛出此异常：

System.ServiceModel.Dispatcher.StreamFormatter.Serialize(XmlDictionaryWriter writer, Object[] parameters, Object returnValue)
System.ServiceModel.Dispatcher.OperationFormatter.SerializeBodyContents(XmlDictionaryWriter writer, MessageVersion version, Object[] parameters, Object returnValue, Boolean isRequest)
System.ServiceModel.Dispatcher.OperationFormatter.OperationFormatterMessage.OperationFormatterBodyWriter.OnWriteBodyContents(XmlDictionaryWriter writer)
System.ServiceModel.Channels.BodyWriter.WriteBodyContents(XmlDictionaryWriter writer)
System.ServiceModel.Channels.BodyWriterMessage.OnWriteBodyContents(XmlDictionaryWriter writer)
System.ServiceModel.Channels.Message.OnWriteMessage(XmlDictionaryWriter writer)
System.ServiceModel.Channels.Message.WriteMessage(XmlDictionaryWriter writer)
System.ServiceModel.Channels.TextMessageEncoderFactory.TextMessageEncoder.WriteMessage(Message message, Stream stream)
System.ServiceModel.Channels.HttpOutput.WriteStreamedMessage(TimeSpan timeout)
System.ServiceModel.Channels.HttpOutput.Send(TimeSpan timeout)
System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.SendRequest(Message message, TimeSpan timeout)
System.ServiceModel.Channels.RequestChannel.Request(Message message, TimeSpan timeout)
System.ServiceModel.Dispatcher.RequestChannelBinder.Request(Message message, TimeSpan timeout)
System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs)
System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)
System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
...UploadDocument(DocumentTransfer request)
...UploadDocument(DocumentTransfer request) in ...

任何想法的人？

Answer 1

当正文为空时，您在SerializeBodyContents中收到错误。

您可以在没有文件时创建不同的操作，也可以在流中放置一个字节以避免异常。如果你不能改变合同，那么第一个选项是可取的，最后一个选项。

Answer 2

另一种选择是返回Stream.Null。