WCF and data contract with template

Question

I've just started to work with WCF and faced with a problem which I cannot handle. I have some code like below.

Data

[DataContract]
public class DataValue<T>
{
    [DataMember] public string Name        { get; set; }
    [DataMember] public T Value            { get; set; }
}

[DataContract]
public class Point : DataValue<float>
{
    public override string ToString()   => $"{Name}\t\t{Value:F2}";
}

and Service

[ServiceContract(SessionMode=SessionMode.Required, CallbackContract = typeof(IServiceCallback))]
[ServiceKnownType(typeof(Point))]
public interface IService
{
    [OperationContract]
    Point[] GetPoints();
}

public sealed class Service : IService
{
    public Point[] GetPoints()
    {
        var p = new [] { new Point { Name = "point_1", Value = 1.1F } };
        return p;
    }
}

When I try to call GetPoints on client side I get an exception

Unhandled Exception: System.ServiceModel.CommunicationException: Error in deserializing body of reply message for operation 'GetPoints'. Unexpected end of file.
 Following elements are not closed: Envelope. ---> System.Xml.XmlException: Unexpected end of file. Following elements are not closed: Envelope.
   at System.Xml.XmlExceptionHelper.ThrowXmlException(XmlDictionaryReader reader, String res, String arg1, String arg2, String arg3)
   at System.Xml.XmlExceptionHelper.ThrowUnexpectedEndOfFile(XmlDictionaryReader reader)
   at System.Xml.XmlBaseReader.MoveToEndOfFile()
   at System.Xml.XmlBinaryReader.ReadNode()
   at System.Xml.XmlBinaryReader.Read()
   at System.Xml.XmlBaseReader.ReadEndElement()
   at System.ServiceModel.Channels.Message.ReadFromBodyContentsToEnd(XmlDictionaryReader reader, EnvelopeVersion envelopeVersion)
   at System.ServiceModel.Dispatcher.OperationFormatter.DeserializeBodyContents(Message message, Object[] parameters, Boolean isRequest)
   at System.ServiceModel.Dispatcher.OperationFormatter.DeserializeReply(Message message, Object[] parameters)
   --- End of inner exception stack trace ---

Server stack trace:
   at System.ServiceModel.Dispatcher.OperationFormatter.DeserializeReply(Message message, Object[] parameters)
   at System.ServiceModel.Dispatcher.ProxyOperationRuntime.AfterReply(ProxyRpc&rpc)
   at System.ServiceModel.Channels.ServiceChannel.HandleReply(ProxyOperationRuntime operation, ProxyRpc& rpc)
   at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
   at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
   at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)

It seems like some kind of serialization problem, I tried to increase net tcp binding buffers (MaxBufferSize, MaxReceivedMessageSize), but it does not help. Are there any ideas how to fix this?

Answer 1

If this error occurs between a .net and mono, then its likely caused by this wcf mono bug

Mono's nettcpbinding implementation was/is wrongly encoding a variable length field. Meaning, that for a .net client, some interface methods calls will work, while others will throw the "Following elements are not closed: Envelope" error, while processing the response from mono.