WCF 服务，由于传入流的“文件意外结束”而引发流异常

Question

我编写了一个交换传输代理，它将电子邮件正文上传到 WCF 服务。该服务与 Exchange 位于同一个盒子上，侦听 localhost:1530 以接收传入的 TCP 连接。传输代理使用 .NET 3.5 框架实现，服务自托管在 .NET 4.0 框架上实现的 Windows 服务中。

我的问题：为什么流在读取完成之前就终止了，我该如何解决？

服务合同定义如下：

[ServiceContract]
public interface IReceiveService
{
    [OperationContract]
    Guid ImportMessage(DateTime dateTimeReceived, string from, IList<string> to, string subject, int attachmentCount, bool bodyEmpty, Guid clientID);

    [OperationContract]
    void ImportMessageBody(IMessageBody body);

    [OperationContract]
    void ImportMessageAttachment(IMessageAttachment attachment);
}

更新：我重新订购了这个，以便人们更容易快速阅读问题，而不必阅读我的其余描述，这很长。第一点显示我如何启动Task 来处理请求似乎是问题所在。事实上，如果我注释掉 Task.Factory.StartNew() 部分，Stream.CopyTo 就可以了。

在我的服务实现中，我尝试使用Stream.CopyTo 将传入流复制到临时文件，如下所示：

public void ImportMessageBody(IMessageBody body)
{
    Task.Factory.StartNew(() =>
        {
            string fileName = GetFileNameFromMagicalPlace();
            using (FileStream fs = new FileStream(fileName, FileMode.Append))
            {
                body.Data.CopyTo(fs); // <---- throws System.IOException right here
            }
        });
}

异常错误为：“错误：读取流时抛出异常。”堆栈跟踪：

   at System.ServiceModel.Dispatcher.StreamFormatter.MessageBodyStream.Read(Byte[] buffer, Int32 offset, Int32 count) 
   at System.IO.Stream.CopyTo...

有一个内部异常：

System.Xml.XmlException: Unexpected end of file. Following elements are not closed: Address, IMessageBody, Body, Envelope. 
    at System.Xml.XmlExceptionHelper.ThrowXmlException(XmlDictionaryReader reader, String res, String arg1, String arg2, String arg3) 
    at System.Xml.XmlBufferReader.GetByteHard() 
    at System.Xml.XmlBufferReader.ReadMultiByteUInt31() 
    at System.Xml.XmlBinaryReader.ReadName(StringHandle handle) 
    at System.Xml.XmlBinaryReader.ReadNode() 
    at System.ServiceModel.Dispatcher.StreamFormatter.MessageBodyStream.Read(Byte[] buffer, Int32 offset, Int32 count) 

其他细节如下。

---

IMessageBody 是这样定义的：

[MessageContract]
public class IMessageBody
{
    [MessageHeader]
    public Guid MessageID { get; set; }

    [MessageHeader]
    public string Format { get; set; }

    [MessageBodyMember]
    public System.IO.Stream Data { get; set; }
}

显示相关位的传输代理的缩写版本（我希望）：

public class Agent : RoutingAgent
{
    public delegate void PostingDelegate(MailItem item);
    IReceiveService service;    

    public Agent()
    {
        string tcpServiceUri = "net.tcp://localhost:1530";

        NetTcpBinding endpointBinding = new NetTcpBinding();
        endpointBinding.TransferMode = TransferMode.Streamed;

        ServiceEndpoint serviceEndpoint = new ServiceEndpoint(
            ContractDescription.GetContract(typeof(IReceiveService)),
            endpointBinding,
            new EndpointAddress(tcpServiceUri));
        ChannelFactory<IReceiveService> factory = new ChannelFactory<IReceiveService>(serviceEndpoint);
        service = factory.CreateChannel();

        this.OnSubmittedMessage += new SubmittedMessageEventHandler(Agent_OnSubmittedMessage);
    }

    void Agent_OnSubmittedMessage(SubmittedMessageEventSource source, QueuedMessageEventArgs e)
    {
        if (TheseAreTheDroidsImLookingFor(e))
        {
            PostingDelegate del = PostData;
            del.BeginInvoke(e.MailItem, CompletePost, GetAgentAsyncContext());
        }
    }

    void PostData(MailItem item)
    {
        // Body class is basically direct implementation of IMessageBody 
        // with a constructor to set up the public properties from MailItem.
        var body = new Body(item); 
        service.ImportMessageBody(body);
    }

    void CompletePost(IAsyncResult ar)
    {
        var context = ar.AsyncState as AgentAsyncContext;
        context.Complete();
    }
}

最后，服务实现是这样托管的：

string queueUri = String.Format("net.tcp://localhost:{0}/{1}", port, serviceName);
            try
            {
                host = new ServiceHost(typeof(ReceiveService), new Uri(queueUri));
                host.AddDefaultEndpoints();
                var endpoint = host.Description.Endpoints.First();
                ((NetTcpBinding)endpoint.Binding).TransferMode = TransferMode.Streamed;                 

                trace.Log(Level.Debug,String.Format("Created service host: {0}", host));                

                host.Open();                
                trace.Log(Level.Debug,"Opened service host.");
            }
            catch (Exception e)
            {
                string message = String.Format("Threw exception while attempting to create ServiceHost for {0}:{1}\n{2}", queueUri, e.Message, e.StackTrace);
                trace.Log(Level.Debug,message);
                trace.Log(Level.Error, message);
            }

Answer 1

好吧，代码太多了。您应该尝试将代码最小化为最小的可重现示例。我想问题可能在这里：

public void ImportMessageBody(IMessageBody body)
{
    Task.Factory.StartNew(() =>
        {
            string fileName = GetFileNameFromMagicalPlace();
            using (FileStream fs = new FileStream(fileName, FileMode.Append))
            {
                body.Data.CopyTo(fs); // <---- throws System.IOException right here
            }
        });
}

默认应用OperationBehavior，此行为包含AutoDisposeParameter，默认设置为true，当操作结束时disposes all disposable parameters。因此，我希望在您的 Task 能够处理整个流之前，操作结束。

Answer 2

问题本质上是我通过调用Task.Factory.StartNew 进行了不必要的并发，而不是通过ServiceBehaviorAttribute 确保我的服务正确配置为并发。感谢 Ladislav 为我指明了正确的方向。