The underlying connection was closed: The connection was closed unexpectedly

If you have a WCF service with inheritance and if have the following error when your WCF client makes a call.


System.ServiceModel.CommunicationException was unhandled

  Message=The underlying connection was closed: The connection was closed unexpectedly.



    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.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.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 ConAppWCFClient.ServiceReference1.ICalculator.Add(ComplexNumber n1, ComplexNumber n2)

       at ConAppWCFClient.ServiceReference1.CalculatorClient.Add(ComplexNumber n1, ComplexNumber n2) in C:\Users\chanmm\AppData\Local\Temporary Projects\ConAppWCFClient\Service References\ServiceReference1\Reference.cs:line 122

       at ConAppWCFClient.Program.Main(String[] args) in C:\Users\chanmm\AppData\Local\Temporary Projects\ConAppWCFClient\Program.cs:line 22

       at System.AppDomain._nExecuteAssembly(RuntimeAssembly 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, Boolean ignoreSyncCtx)

       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)

       at System.Threading.ThreadHelper.ThreadStart()

  InnerException: System.Net.WebException

       Message=The underlying connection was closed: The connection was closed unexpectedly.



            at System.Net.HttpWebRequest.GetResponse()

            at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout)





Most like you miss one important attribute when you are doing inheritance. The KnownType attribute.

See the code below.






  publicdouble Real = 0.0D;


  publicdouble Imaginary = 0.0D;


  public ComplexNumber(double real, double imaginary)


    this.Real = real;

    this.Imaginary = imaginary;





publicclassComplexNumberWithMagnitude : ComplexNumber


  public ComplexNumberWithMagnitude(double real, double imaginary) : base(real, imaginary) { }



  publicdouble Magnitude


    get { returnMath.Sqrt(Imaginary * Imaginary + Real * Real); }

    set { thrownewNotImplementedException(); }




Download the complete code from sample file name is WCFKnownType.rar. My MSN ID is



About chanmingman

Since March 2011 Microsoft Live Spaces migrated to Wordpress ( till now, I have is over 1 million viewers. This blog is about more than 50% telling you how to resolve error messages, especial for Microsoft products. The blog also has a lot of guidance teaching you how to get stated certain Microsoft technologies. The blog also uses as a help to keep my memory. The blog is never meant to give people consulting services or silver bullet solutions. It is a contribution to the community. Thanks for your support over the years. Ming Man is Microsoft MVP since year 2006. He is a software development manager for a multinational company. With 25 years of experience in the IT field, he has developed system using Clipper, COBOL, VB5, VB6, VB.NET, Java and C #. He has been using Visual Studio (.NET) since the Beta back in year 2000. He and the team have developed many projects using .NET platform such as SCM, and HR based applications. He is familiar with the N-Tier design of business application and is also an expert with database experience in MS SQL, Oracle and AS 400.
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