silverlightFaultBehavior for WCF - but still getting code 500 - silverlight

Question

I want to get a meaningful error message from my WCF service for my Silverlight 4 application. After some investigation, I found that I need to change the reply code from 500 to 200 if I want silverlight enable to read the meaningful error message. Here is the article: http://msdn.microsoft.com/de-de/library/ee844556(VS.95).aspx
I have implemented it as it is written there, the application compiles and I can use the service - but I still get the 500 return code. The main difference I see is that I call the service via HTTPS not HTTP. Maybe this is the reason, why it doesn't work? Any idea, how to get the return code 200?
Here is my Web.Config:
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<configSections>
<sectionGroup name="applicationSettings" type="System.Configuration.ApplicationSettingsGroup, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
<section name="ServiceConfiguratorDataSource.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
</sectionGroup>
</configSections>
<system.web>
<compilation debug="true" targetFramework="4.0" />
</system.web>
<system.serviceModel>
<extensions>
<behaviorExtensions>
<add name="silverlightFaults" type="ServiceConfiguratorDataSource.SilverlightFaultBehavior, ServiceConfiguratorDataSource, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"/>
</behaviorExtensions>
</extensions>
<services>
<service name="ServiceConfiguratorDataSource.Service" behaviorConfiguration="ServiceConfiguratorDataSourceBehaviour">
<endpoint address="" binding="customBinding" behaviorConfiguration="SLFaultBehavior" bindingConfiguration="ServiceConfiguratorCustomBinding" contract="ServiceConfiguratorDataSource.IService" />
</service>
</services>
<bindings>
<customBinding>
<binding name="ServiceConfiguratorCustomBinding">
<security authenticationMode="UserNameOverTransport"></security>
<binaryMessageEncoding></binaryMessageEncoding>
<httpsTransport/>
</binding>
</customBinding>
</bindings>
<behaviors>
<serviceBehaviors>
<behavior name="ServiceConfiguratorDataSourceBehaviour">
<serviceMetadata httpsGetEnabled="true" />
<serviceDebug includeExceptionDetailInFaults="True"/>
<serviceCredentials>
<userNameAuthentication userNamePasswordValidationMode="Custom" customUserNamePasswordValidatorType="ServiceConfiguratorDataSource.UserCredentialsValidator,ServiceConfiguratorDataSource" />
</serviceCredentials>
</behavior>
</serviceBehaviors>
<endpointBehaviors>
<behavior name="SLFaultBehavior">
<silverlightFaults/>
</behavior>
</endpointBehaviors>
</behaviors>
<serviceHostingEnvironment multipleSiteBindingsEnabled="true" />
</system.serviceModel>
<system.webServer>
<modules runAllManagedModulesForAllRequests="true"/>
</system.webServer>
</configuration>
... and here the silverlightFaultBehavior.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.ServiceModel.Configuration;
using System.ServiceModel.Description;
using System.ServiceModel.Dispatcher;
using System.ServiceModel.Channels;
using System.ServiceModel;
namespace ServiceConfiguratorDataSource
{
public class SilverlightFaultBehavior : BehaviorExtensionElement, IEndpointBehavior
{
public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
{
SilverlightFaultMessageInspector inspector = new SilverlightFaultMessageInspector();
endpointDispatcher.DispatchRuntime.MessageInspectors.Add(inspector);
}
public class SilverlightFaultMessageInspector : IDispatchMessageInspector
{
public void BeforeSendReply(ref Message reply, object correlationState)
{
if (reply.IsFault)
{
HttpResponseMessageProperty property = new HttpResponseMessageProperty();
// Here the response code is changed to 200.
property.StatusCode = System.Net.HttpStatusCode.OK;
reply.Properties[HttpResponseMessageProperty.Name] = property;
}
}
public object AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext)
{
// Do nothing to the incoming message.
return null;
}
}
// The following methods are stubs and not relevant.
public void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters)
{
}
public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime)
{
}
public void Validate(ServiceEndpoint endpoint)
{
}
public override System.Type BehaviorType
{
get { return typeof(SilverlightFaultBehavior); }
}
protected override object CreateBehavior()
{
return new SilverlightFaultBehavior();
}
}
}
Someone knows if this is because of https ... and if so, how to get it to work?
Thanks in advance,
Frank
EDITH says: I just have added some logging: the ApplyDispatchBehavior - method is called, but the BeforeSendReply - method not ... any ideas why?

Answer 1

If I remember correctly, the UserNamePasswordValidator gets called very early in the pipeline, before the dispatcher ever gets called, which is why your custom dispatch behavior isn't affecting anything. (The reason is security: WCF wants to "throw out" unauthorized requests as early as possible, while running as little code as possible for them).
As you yourself suggested in the comments, one solution would be to just validate the credentials later in the pipeline - e.g. in every operation (or maybe even in a message inspector's AfterReceiveRequest?)