//add a reference to "Elmah.dll"
using System;
using System.ServiceModel.Channels;
using System.ServiceModel.Dispatcher;
using System.Web;

namespace ElmahWcf
{
   public class HttpErrorHandler : IErrorHandler
   {
       #region IErrorHandler Members
       public bool HandleError(Exception error)
       {
           return false;
       }

       public void ProvideFault(Exception error, MessageVersion version, ref Message fault)
       {
           if (error == null)
               return;

           if (HttpContext.Current == null) //In case we run outside of IIS
               return;

           Elmah.ErrorSignal.FromCurrentContext().Raise(error);
       }
       #endregion
   }
}

//add a ref to "System.ServiceModel" assembly
using System;
using System.Collections.ObjectModel;
using System.ServiceModel;
using System.ServiceModel.Channels;
using System.ServiceModel.Description;
using System.ServiceModel.Dispatcher;

namespace ElmahWcf
{
   public class ServiceErrorBehaviorAttribute : Attribute, IServiceBehavior
   {
       Type errorHandlerType;
       public ServiceErrorBehaviorAttribute(Type errorHandlerType)
       {
           this.errorHandlerType = errorHandlerType;
       }

       #region IServiceBehavior Members

       public void AddBindingParameters(
           ServiceDescription serviceDescription,
           ServiceHostBase serviceHostBase, Collection<ServiceEndpoint> endpoints,
           BindingParameterCollection bindingParameters)
       { }

       public void ApplyDispatchBehavior(
           ServiceDescription serviceDescription,
           ServiceHostBase serviceHostBase)
       {
           IErrorHandler errorHandler;
           errorHandler = (IErrorHandler)Activator.CreateInstance(errorHandlerType);
           foreach (ChannelDispatcherBase cdb in serviceHostBase.ChannelDispatchers)
           {
               ChannelDispatcher cd = cdb as ChannelDispatcher;
               cd.ErrorHandlers.Add(errorHandler);
           }
       }

       public void Validate(
           ServiceDescription serviceDescription,
           ServiceHostBase serviceHostBase)
       { }
       #endregion
   }
}

    [ServiceErrorBehavior(typeof(HttpErrorHandler))] //Integrating with ELMAH
   [EnableClientAccess()]
   public partial class MyDomainService : LinqToEntitiesDomainService<myEntities>

<?xml version="1.0" encoding="utf-8"?>
<configuration>
 <configSections>
   <sectionGroup name="elmah">
     <section name="security" requirePermission="false" type="Elmah.SecuritySectionHandler, Elmah"/>
     <section name="errorLog" requirePermission="false" type="Elmah.ErrorLogSectionHandler, Elmah" />
     <section name="errorMail" requirePermission="false" type="Elmah.ErrorMailSectionHandler, Elmah" />
     <section name="errorFilter" requirePermission="false" type="Elmah.ErrorFilterSectionHandler, Elmah"/>
     <section name="errorTweet" requirePermission="false" type="Elmah.ErrorTweetSectionHandler, Elmah"/>
   </sectionGroup>
 </configSections>

 <elmah>
   <security allowRemoteAccess="1" />
   <errorLog type="Elmah.XmlFileErrorLog, Elmah" logPath="~/Errors" />
   <!-- <errorMail
       from="errors@site.net"
       to="nasiri@site.net"
       subject="prj-error"
       async="true"
       smtpPort="25"
       smtpServer="mail.site.net"
       noYsod="true" /> -->
 </elmah>

 <system.webServer>
   <modules runAllManagedModulesForAllRequests="true">
     <add name="ErrorLog" type="Elmah.ErrorLogModule, Elmah"/>
     <add name="DomainServiceModule"
          preCondition="managedHandler"
          type="System.ServiceModel.DomainServices.Hosting.DomainServiceHttpModule, System.ServiceModel.DomainServices.Hosting, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />
   </modules>
   <validation validateIntegratedModeConfiguration="false" />
   <handlers>
     <add name="Elmah" verb="POST,GET,HEAD" path="myelmah.axd" type="Elmah.ErrorLogPageFactory, Elmah" />
   </handlers>
 </system.webServer>
 <system.web>
   <globalization
       requestEncoding="utf-8"
       responseEncoding="utf-8"
  />
   <authentication mode="Forms">
     <!--one month ticket-->
     <forms name=".403AuthV"
            cookieless="UseCookies"
            slidingExpiration="true"
            protection="All"
            path="/"
            timeout="43200" />
   </authentication>
   <httpHandlers>
     <add verb="POST,GET,HEAD" path="myelmah.axd" type="Elmah.ErrorLogPageFactory, Elmah" />
   </httpHandlers>
   <httpModules>
     <add name="ErrorLog" type="Elmah.ErrorLogModule, Elmah"/>
     <add name="DomainServiceModule"
          type="System.ServiceModel.DomainServices.Hosting.DomainServiceHttpModule, System.ServiceModel.DomainServices.Hosting, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />
   </httpModules>
   <compilation debug="true" targetFramework="4.0">
     <assemblies>
       <add assembly="System.Data.Entity, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
     </assemblies>
   </compilation>
 </system.web>
 <connectionStrings>
 </connectionStrings>
 <system.serviceModel>
   <serviceHostingEnvironment
     aspNetCompatibilityEnabled="true"
     multipleSiteBindingsEnabled="true" />
 </system.serviceModel>
</configuration>

throw new Exception("This is an ELMAH test");

[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]