Complex data types in WCF?

问题:

I've run into a problem trying to return an object that holds a collection of childobjects that again can hold a collection of grandchild objects. I get an error, 'connection forcibly closed by host'.

Is there any way to make this work? I currently have a structure resembling this:

pseudo code:

Person:
IEnumerable<Order>

Order:
IEnumerable<OrderLine>

All three objects have the DataContract attribute and all public properties i want exposed (including the IEnumerable's) have the DataMember attribute.

I have multiple OperationContract's on my service and all the methods returning a single object OR an IEnumerable of an object works perfectly. It's only when i try to nest IEnumerable that it turns bad. Also in my client service reference i picked the generic list as my collection type. I just want to emphasize, only one of my operations/methods fail with this error - the rest of them work perfectly.

EDIT (more detailed error description):

[SocketException (0x2746): An existing connection was forcibly closed by
the remote host]
[IOException: Unable to read data from the transport connection:
An existing connection was forcibly closed by the remote host.]
[WebException: The underlying connection was closed: An unexpected
error occurred on a receive.]
[CommunicationException: An error occurred while receiving the HTTP
response to http://myservice.mydomain.dk/MyService.svc. 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.]

I tried looking for logs but i can't find any... also i'm using a WSHttpBinding and an http endpoint.

回答1:

As a note, you need to learn how to use the WCF logging utilities:

Logging info.

Config Editor (makes it a snap to setup).

Trace viewer. Totally awesome. Allows multiple services (client and server) to trace and can join them and help you analyse all the details. Lets you get to the root of issues really fast. (Cause when there's a server WCF error, the client is unlikely to get useful data out.)

回答2:

Ok i finally found the real problem in my case. It seems exposing enums is not the greatest thing in the world. I either have to set a default value on them, or instead expose the property as an int or whatever integer-type my enum is based on.

Thanks for helping, you had no way of knowing this - i found the enums on the 3rd level in my structure and systematicly removing datamembers one by one was the way i found out. It seems i'm not the only one who ran into this problem - this guy obviously had similar problems :)

http://zianet.dk/blog/2007/11/24/serializing-enums-in-wcf/

回答3:

If you are working with WCF+(EF+POCO) then try setting,

ObjectContext.ContextOptions.LazyLoadingEnabled = false;
ObjectContext.ContextOptions.ProxyCreationEnabled = false;

回答4:

Add this line into <system.web/>:

<httpRuntime maxRequestLength="102400" executionTimeout="3600" />

回答5:

Enums get a DataContract attribute, like any class would, but the enum values aren't supposed to have DataMember attributes on them.

Change them to EnumMember and you'll stop getting this inscrutable error.

回答6:

this is actually the same information as your first exception description. it would be interesing what the original cause for the socketexception was. it has to be some type of error in the service itself. can you locate where exactly whar exception happens?

i had similar errors when trying to return normal IEnumerables that were overwritten (they were marked as virtual) by NHibernate, and substitued with GenericPersistentBag, which is not serializable. have you marked your IEnumerable datamembers as virtual due to nhibernate or something similar? this could explain your error.

btw. wcf exceptions are often quite meaningless (which can be very frustrating when tracking down a bug ;)

回答7:

I have had the same problem too (.Net 3.5). Turns out my base class DataContract was missing a known type. It's unfortunate that the WCF error was not more descriptive.

回答8:

did you specify in your service behavior config? it seems like some information is missing in this stacktrace.

can you grab the exception at server side (e.g. in visual studio debug mode or with a logging library like log4net).

have you tried calling some other methods (simple helloworld() e.g.) on the same service to be sure that the service configuration itself works? this kind of exceptino could also indicate some serialization problems. what types do you want to send over the wire? do you use KnownType's somewhere?

回答9:

Server Error in '/' Application.
--------------------------------------------------------------------------------

An existing connection was forcibly closed by the remote host 
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host

Source Error: 

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.  

Stack Trace: 


[SocketException (0x2746): An existing connection was forcibly closed by the remote host]
   System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags) +93
   System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size) +119

[IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.]
   System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size) +267
   System.Net.PooledStream.Read(Byte[] buffer, Int32 offset, Int32 size) +25
   System.Net.Connection.SyncRead(HttpWebRequest request, Boolean userRetrievedStream, Boolean probeRead) +306

[WebException: The underlying connection was closed: An unexpected error occurred on a receive.]
   System.Net.HttpWebRequest.GetResponse() +1532114
   System.ServiceModel.Channels.HttpChannelRequest.WaitForReply(TimeSpan timeout) +40

[CommunicationException: An error occurred while receiving the HTTP response to http://Zzzstrukturservice.xxx.dk/ZzzstrukturService.svc. 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.]
   System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg) +2668969
   System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type) +717
   xxx.Services.ZzzstrukturServiceClient.ZzzstrukturServiceProxy.IZzzstrukturService.GetMatrixSet(Int32 matrixSetId) +0
   xxx.Services.ZzzstrukturServiceClient.ZzzstrukturRepository.GetMatrixSetById(Int32 matrixSetId) in f:\ccnet\work\xxx.Zzzstruktur\1. Presentation Layer\ZzzstrukturServiceClient\ZzzstrukturRepository.cs:90
   xxx.yyy.yyyWeb.AnnoncePage.OnLoad(EventArgs e) in f:\ccnet\work\yyyV2\1. Presentation Layer\yyyWeb\Annonce.aspx.cs:40
   System.Web.UI.Control.LoadRecursive() +47
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1436




--------------------------------------------------------------------------------
Version Information: Microsoft .NET Framework Version:2.0.50727.1433; ASP.NET Version:2.0.50727.1433 

回答10:

I don't know why this can happen. but i also had similar problems.

I have changed my enums.remove the indexes(e.g. ASNOrder = 1, -> ASNOrder,),and no error occoured.

回答11:

Don't return the literal IEnumerable in a contract, there is the famous WCF IEnumerable bug

回答12:

Try setting [OperationBehavior()] above your implementation of the interface method.

回答13:

I've had this error when using 'yield return' to build up an enumeration of objects mapped to my DataContract type.

Calling ToList / ToArray on the yield results fixed the issue and the service call worked correctly.

回答14:

Yep, I had the same problem here and it was todo with returning objects that had enum values in it. Changed the DataMember to an int and everything statrted working.