WCF Test Client Error Failed to invoke the service ( while Sending Entities Through WCF)

Question

I have a Service where all methods work fine except one which returns a list

My Module Class (An Entity) is as follow

[DataContract(IsReference = true)] //prevents Infinite loop
[KnownType(typeof(SubModule))]
public class ModuleMst 
{
    public ModuleMst ()
    { }

    [Key]
    [DataMember]
    public int moduleid { get; set; }

    [StringLength(100)]
    [DataMember]
    public string modulename { get; set; }

    [StringLength(1)]
    [DataMember]
    public string status { get; set; }

    [DataMember]
    public string crby { get; set; }

    [DataMember]
    public DateTime crdt { get; set; }

    [DataMember]
    public string modby { get; set; }

    [DataMember]
    public DateTime moddt { get; set; }

    //[DataMember]
    public virtual List SubModules { get; set; }

}

The Exception WcfTestClient shows as

An error occurred while receiving the HTTP response to http://localhost:8888/ArchService/. This could be due to the service endpoint binding not using the HTTP protocol. This could also be due to an HTTP request context being aborted by the server (possibly due to the service shutting down). See server logs for more details.

Server stack trace: 
   at System.ServiceModel.Channels.HttpChannelUtilities.ProcessGetResponseWebException(WebException webException, HttpWebRequest request, HttpAbortReason abortReason)
   at System.ServiceModel.Channels.HttpChannelFactory`1.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 IArchService.GetAllModules()
   at ArchServiceClient.GetAllModules()

Inner Exception:
The underlying connection was closed: An unexpected error occurred on a receive.
   at System.Net.HttpWebRequest.GetResponse()
   at System.ServiceModel.Channels.HttpChannelFactory`1.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout)

Inner Exception:
Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.
   at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
   at System.Net.PooledStream.Read(Byte[] buffer, Int32 offset, Int32 size)
   at System.Net.Connection.SyncRead(HttpWebRequest request, Boolean userRetrievedStream, Boolean probeRead)

Inner Exception:
An existing connection was forcibly closed by the remote host
   at System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags)
   at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)

The Configuration being

The Exception is not being very helpful.

Also All of the bindings fail with this particular method.

What did i miss ?

EDIT

It seems like any method that tries to return a List (where T can be any entity )fails with the error An existing connection was forcibly closed by the remote host

EDIT

Client Configuration is as follow

EDIT 3

My Other Related Entity Classes are causing the error. I dont know why. Here are they

[Table("SubModuleMst", Schema = "setp")]
[DataContract(IsReference = true)] //prevents Infinite loop
[KnownType(typeof(ModuleMst))]
[KnownType(typeof(List))]

public class SubModule
{
    public SubModule()
    { }

    #region SubModule

    [Key]
    [DataMember]
    public int submoduleid { get; set; }
     [DataMember]
    public int moduleid { get; set; }
    [DataMember]
    [StringLength(100)]
    public string submodulename { get; set; }
    [DataMember]
    public int orderno { get; set; }
    [DataMember]
    [StringLength(1)]
    public string status { get; set; }
    [DataMember]
    public string crby { get; set; }
    [DataMember]
    public DateTime crdt { get; set; }
    [DataMember]
    public string modby { get; set; }
    [DataMember]
    public DateTime moddt { get; set; }
    #endregion

    [DataMember]
    public virtual ModuleMst Module { get; set; }
    [DataMember]
    public virtual List Pages { get; set; }
}

[Table("PageMst", Schema = "setp")]
[DataContract(IsReference = true)] //prevents Infinite loop
[KnownType(typeof(SubModule))]
public class PageMst
{
    public PageMst()
    { }

    #region PageMst

    [Key]
    [DataMember]
    public int pageid { get; set; }
    [DataMember]
    [Required]
    [ForeignKey("SubModule")]
    public int submoduleid { get; set; }
    [DataMember]
    [StringLength(1000)]
    [Required]
    public string pagename { get; set; }
    [DataMember]
    [StringLength(1000)]
    public string pageurl { get; set; }
    [DataMember]
    public int orderno { get; set; }
    [DataMember]
    [StringLength(1)]
    public string menuitm { get; set; }
    [DataMember]
    public int rptparentid { get; set; }
    [DataMember]
    [StringLength(1)]
    public string alertflag { get; set; }
    [DataMember]
    [StringLength(1)]
    public string status { get; set; }
    [DataMember]
    public string crby { get; set; }
    [DataMember]
    public DateTime crdt { get; set; }
    [DataMember]
    public string modby { get; set; }
    [DataMember]
    public DateTime moddt { get; set; }
    [DataMember]
    [StringLength(200)]
    public string paramids { get; set; }
    [DataMember]
    [StringLength(500)]
    public string repurl { get; set; }
    #endregion

    [DataMember]
    public virtual SubModule SubModule { get; set; }
}

EDIT 4

Now I am confirmed that the error is due to The Proxy created by EF are Not Serializable as such According to this MSDN Article https://msdn.microsoft.com/en-us/library/ee705457(v=vs.100).aspx And Also according to this SO Article

Deb · Accepted Answer

Since nobody answered my question, I am posting here what i did to make it work in the hope that it will help somebody else like me.

It turns out that the POCO proxy type cannot be directly serialized or deserialized by the Windows Communication Foundation (WCF) as per this MSDN Article.

This is because EF creates a Wrapper around the POCO for Entity Tracking which is not the same class as the POCO class and hence WCF can not serialize it since it can only serialize known Types.

So in order to make entities Serializable through WCF one of the following needs to be done.

Disable Proxy creation in the DBContext Configuration. (See this )
Use .AsNoTracking() (See this SO Post)
Use an Attribute to decorate your service methods that return Entities using ProxyDataContractResolver (See above MSDN article for a Walkthrough)

I used the 3rd approach and my service returns POCO Entities finally. The code in the walkthrough article is self explanatory so not posting here.

And at last i think DTOs are the best way to go as far as EF is considered.

WCF Test Client Error Failed to invoke the service ( while Sending Entities Through WCF)

Answers (1)

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