The solution from my blog post (referenced in the OP) was based on an existing solution we were/are using to alter HTTP Response Codes during an error state.
So, for us it was a one-line change to pass the Exception to ELMAH. If there's a better solution, I'd love to know about it too.
For Posterity/Reference, and potential improvement - here's the code from the current solution.
using System;
using System.ServiceModel;
using System.ServiceModel.Dispatcher;
using System.ServiceModel.Channels;
using System.ServiceModel.Description;
using System.Collections.ObjectModel;
using System.Net;
using System.Web;
using Elmah;
namespace YourApplication
{
/// <summary>
/// Your handler to actually tell ELMAH about the problem.
/// </summary>
public class HttpErrorHandler : IErrorHandler
{
public bool HandleError(Exception error)
{
return false;
}
public void ProvideFault(Exception error, MessageVersion version, ref Message fault)
{
if (error != null ) // Notify ELMAH of the exception.
{
if (System.Web.HttpContext.Current == null)
return;
Elmah.ErrorSignal.FromCurrentContext().Raise(error);
}
}
}
/// <summary>
/// So we can decorate Services with the [ServiceErrorBehaviour(typeof(HttpErrorHandler))]
/// ...and errors reported to ELMAH
/// </summary>
public class ServiceErrorBehaviourAttribute : Attribute, IServiceBehavior
{
Type errorHandlerType;
public ServiceErrorBehaviourAttribute(Type errorHandlerType)
{
this.errorHandlerType = errorHandlerType;
}
public void Validate(ServiceDescription description, ServiceHostBase serviceHostBase)
{
}
public void AddBindingParameters(ServiceDescription description, ServiceHostBase serviceHostBase, Collection<ServiceEndpoint> endpoints, BindingParameterCollection parameters)
{
}
public void ApplyDispatchBehavior(ServiceDescription description, ServiceHostBase serviceHostBase)
{
IErrorHandler errorHandler;
errorHandler = (IErrorHandler)Activator.CreateInstance(errorHandlerType);
foreach (ChannelDispatcherBase channelDispatcherBase in serviceHostBase.ChannelDispatchers)
{
ChannelDispatcher channelDispatcher = channelDispatcherBase as ChannelDispatcher;
channelDispatcher.ErrorHandlers.Add(errorHandler);
}
}
}
}
Decorate your WCF Services with the ServiceErrorBehaviour Attribute:
[ServiceContract(Namespace = "http://example.com/api/v1.0/")]
[ServiceErrorBehaviour(typeof(HttpErrorHandler))]
public class MyServiceService
{
// ...
}
When creating a BehaviorExtensionElement it is even possible to activate the behavior using config:
public class ErrorBehaviorExtensionElement : BehaviorExtensionElement
{
public override Type BehaviorType
{
get { return typeof(ServiceErrorBehaviourAttribute); }
}
protected override object CreateBehavior()
{
return new ServiceErrorBehaviourAttribute(typeof(HttpErrorHandler));
}
}
Config:
<system.serviceModel>
<extensions>
<behaviorExtensions>
<add name="elmah" type="Namespace.ErrorBehaviorExtensionElement, YourAssembly, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"/>
</behaviorExtensions>
</extensions>
<behaviors>
<serviceBehaviors>
<behavior>
<elmah />
</behavior>
</serviceBehaviors>
</behaviors>
</system.serviceModel>
That way it is also possible to use ELMAH in combination with RIA services!
This may well be obvious to some people but I just spent quite a while trying to figure out why my HttpContext.Current was null despite following all of Will Hughes' excellent answer. Embarassingly, I realised that this was because my WCF service is activated by a MSMQ message.
I ended up rewriting the ProvideFault()
method:
if (HttpContext.Current == null)
{
ErrorLog.GetDefault(null).Log(new Error(error));
}
else
{
ErrorSignal.FromCurrentContext().Raise(error);
}
I have done this based on Will's work but I want to verify that this is the correct approach before posting the code.
I think this is a great approach (kudos to Will for this posting!). I don't think Will or you have missed anything here. Implementing IErrorHandler is the preferred way of capturing all possible server-side exceptions that could otherwise cause the communication channel to be faulted (torn down) and thus it's a natural place to hook in some logging like ELMAH.
Marc
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With