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Asked: 2026-05-15T22:58:31+00:00

I have a quite simple WCF service method which returns an IQueryable, just for

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I have a quite simple WCF service method which returns an IQueryable, just for testing. Perhaps I got something wrong when trying to understand what IQueryable is designed for. I clearly plan to use this with the IQueryable provider of NHibernate later. But first I ran into some sort of serialization problems (at least I think it might be the problem) whenever using a WCF method returning an IQueryable. It doesn’t even work for a simple string.

Here’s my code:

public IQueryable<string> GetEquipmentConfigurations()
{
  var returnValue = new List<string>();
  returnValue.Add("test");
  return returnValue.AsQueryable();
}

It might not have much sense, it’s just for testing whether I really get those IQueryables over the wire using WCF. Whenever I call this method using a client like SoapUI I get a socket exception and a connection reset, just the same as if I was trying to return something that is not marked as DataContract. But the only thing I do here is trying to return some lousy string list. What’s wrong with that?

I use basicHTTPBinding, here are my settings: 

<system.serviceModel>
   <services>
      <service name="EquipmentConfigurationService" behaviorConfiguration="DefaultBehavior">
        <host>
          <baseAddresses>
            <add baseAddress="http://localhost:8000/Krones.KBase/Services/EquipmentConfigurationService"/>
          </baseAddresses>
        </host>
        <endpoint address=""
                  binding="basicHttpBinding"
                  contract="Krones.MES.KBase.Public.Service.EquipmentDefinition.IEquipmentConfigurationService" />
        <endpoint address="mex"
                  binding="mexHttpBinding"
                  contract="IMetadataExchange" />
      </service>
   </services>
   <behaviors>
      <serviceBehaviors>
         <behavior name="DefaultBehavior">
            <serviceMetadata httpGetEnabled="True"/>
            <serviceDebug includeExceptionDetailInFaults="True"/>
         </behavior>
      </serviceBehaviors>
   </behaviors>
</system.serviceModel>

The OperationContract attribute is set for the interface:

[OperationContract]
IQueryable<string> GetEquipmentConfigurations();

It all works well when just returning a simple string. Anyway I want to take profit from the IQueryable features using LINQ later.

Anybody any idea what’s going wrong here?

Thanks and Cheers,

Stefan

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1 Answer

  1. Editorial Team

    (Obsolete)
    AFAIK it isn’t possible out of the box to serialize IQueryable<> or Expression Trees (think about it – it would mean that the expression tree / lambda would need to be serialized and the function rebuilt)

    However, where there is a will, it seems there is a way – you might want to look at projects such as this
    http://code.msdn.microsoft.com/exprserialization

    Edit : Note that times have changed – See WCF RIA Services as per Marc Gravell’s post.

    Good luck!

    HTH

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