How to create a global exception handler for WCF services?

Question

I want to log all exceptions on the server side .

In ASP.NET, I write something similar in Global.asax.cs, but will this work for the WCF service too?

public class Global : HttpApplication { protected void Application_Error(object sender, EventArgs e) { Exception unhandledException = Server.GetLastError(); //Log exception here ... } } 

UPDATE: I don't want to try ... grab onto every [OperationContract] in my .svc file. I briefly ... I want to make sure that all exceptions that my services raise are logged by log4net. I'm not talking about how the client handles the exception.

Answer 1

You can create a WCF error logger by running IErrorHandler and linking it to the service; usually (for logging) you return false from a HandleError (letting other handlers execute) and HandleError error either in HandleError (using Exception ) or in ProvideFault (using ref Message fault ).

I apply this handler by creating my own behavior (inheriting from BehaviorBase ), which (in ApplyDispatchBehavior ) adds an error handler to endpointDispatcher.ChannelDispatcher.ErrorHandlers if it does not already exist.

Behavior can be applied through configuration.

Answer 2

Initially, to this problem and after many open tabs in research, including articles related to other answers, here is exactly what someone needs for this.

Here is the ErrorHandler class ...

 Imports System.ServiceModel.Configuration Imports System.ServiceModel.Description Imports System.ServiceModel.Dispatcher ''' <summary> ''' This class defines a global ErrorHandler, that allows us to control the ''' fault message returned to the client and perform custom error processing ''' like logging. ''' </summary> Public Class ErrorHandler Implements IErrorHandler ''' <summary> ''' This method will be called whenever an exception occurs. Therefore, ''' we log it and then return false so the error can continue to propagate up the chain. ''' </summary> ''' <param name="ex">Exception being raised.</param> ''' <returns>False to let the error propagate up the chain, or True to stop the error here.</returns> Public Function HandleError(ByVal ex As Exception) As Boolean Implements IErrorHandler.HandleError 'Unknown error occurred at the Service layer, log the event logEvent("Encountered an unknown error at the Service layer.", ex, EventLogEntryType.Error) Return False End Function ''' <summary> ''' This method is optionally used to transform standard exceptions into custom ''' FaultException(Of TDetail) that can be passed back to the service client. ''' </summary> ''' <param name="ex">Exception being raised.</param> ''' <param name="version">SOAP version of the message.</param> ''' <param name="fault">Message object that is returned to the client.</param> Public Sub ProvideFault(ByVal ex As Exception, ByVal version As Channels.MessageVersion, ByRef fault As Channels.Message) Implements IErrorHandler.ProvideFault End Sub End Class ''' <summary> ''' This class defines a ServiceBehavior, that will allow us to add our ''' custom ErrorHandler class, defined above, to each channel we have a ''' service running on. ''' </summary> Public Class ErrorServiceBehavior Implements IServiceBehavior Public Sub AddBindingParameters(serviceDescription As ServiceDescription, serviceHostBase As ServiceHostBase, endpoints As ObjectModel.Collection(Of ServiceEndpoint), bindingParameters As Channels.BindingParameterCollection) Implements IServiceBehavior.AddBindingParameters End Sub Public Sub ApplyDispatchBehavior(serviceDescription As ServiceDescription, serviceHostBase As ServiceHostBase) Implements IServiceBehavior.ApplyDispatchBehavior 'Enumerate all channels and add the error handler to the collection Dim handler As New ErrorHandler() For Each dispatcher As ChannelDispatcher In serviceHostBase.ChannelDispatchers dispatcher.ErrorHandlers.Add(handler) Next End Sub Public Sub Validate(serviceDescription As ServiceDescription, serviceHostBase As ServiceHostBase) Implements IServiceBehavior.Validate End Sub End Class ''' <summary> ''' This class defines a BehaviorExtensionElement, so that we can ''' use the ErrorServiceBehavior class, defined above, in our App.config. ''' </summary> Public Class ErrorHandlerBehavior Inherits BehaviorExtensionElement Protected Overrides Function CreateBehavior() As Object Return New ErrorServiceBehavior() End Function Public Overrides ReadOnly Property BehaviorType As Type Get Return GetType(ErrorServiceBehavior) End Get End Property End Class 

Then these sections need to be added / updated in the App.config file for your maintenance project ...

 <system.serviceModel> <extensions> <behaviorExtensions> <!-- Add in our custom error handler --> <add name="ErrorLogging" type="Service.ErrorHandlerBehavior, Service, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" /> </behaviorExtensions> </extensions> <services> <service name="Service.Service" behaviorConfiguration="Service.ServiceBehavior"> <endpoint address="" binding="wsHttpBinding" bindingConfiguration="wsHttp" contract="SentinelService.IService"/> <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" /> </service> </services> <behaviors> <serviceBehaviors> <behavior name="Service.ServiceBehavior"> <serviceMetadata httpGetEnabled="True" /> <serviceDebug includeExceptionDetailInFaults="False" /> <!-- Add in our custom error handler, from behaviorExtensions element --> <ErrorLogging /> </behavior> </serviceBehaviors> </behaviors> 

In particular, it is necessary to add an element of behavior, its name must be added to the section of behavior, it is necessary that the section of behavior be named, and this section of behavior must be a behavior. Configuration for the service.

Be careful with the "type" attribute in the behavior area, although this should be accurate. If you are not sure, you can use the following to determine its GetType(ErrorHandlerBehavior).AssemblyQualifiedName .

If you are interested, this is the code behind the logEvent function that I use ...

 ''' <summary> ''' Logs a message and optional exception to the application event log. ''' </summary> ''' <param name="message">String message to log.</param> ''' <param name="ex">Exception to log.</param> ''' <param name="eventType">EventLogEntryType indicating the message severity.</param> Public Sub logEvent(ByVal message As String, Optional ByVal ex As Exception = Nothing, _ Optional ByVal eventType As EventLogEntryType = EventLogEntryType.Information) 'Initialize report Dim report As String = message + vbNewLine + vbNewLine 'Create eventLogger Dim eventLogger As New EventLog() 'Register event source, add any Exception information to the report, and then log it Try 'Register the app as an Event Source If Not EventLog.SourceExists("MyAppName") Then EventLog.CreateEventSource("MyAppName", "Application") End If If ex IsNot Nothing Then 'Force eventType to error eventType = EventLogEntryType.Error 'Add Exception Information to report report += "Exception Information:" + vbNewLine Dim currentException As Exception = ex Dim exCount As Integer = 1 While (currentException IsNot Nothing) report += Space(5) + If(exCount = 1, "Message:", "Inner Exception:") + vbNewLine report += Space(10) + currentException.Message + vbNewLine report += Space(5) + "StackTrace:" + vbNewLine report += Space(10) + currentException.StackTrace + vbNewLine report += vbNewLine currentException = currentException.InnerException exCount += 1 End While End If Catch reportException As Exception 'This catch ensures that no matter what some error report is logged. report += vbNewLine + vbNewLine + "PARTIAL REPORT!!!...AN ERROR WAS ENCOUNTERED GENERATING ERROR REPORT." Finally Try 'Log report eventLogger.Source = "MyAppName" eventLogger.WriteEntry(report, eventType) Catch logEventException As Exception 'Eat it...nothing can be done at this point and we do 'not want the application to crash over an error report 'if we can prevent it End Try End Try End Sub 

Answer 3

This is not the answer itself, but an addition to the big answer provided by SkyBlade002 , providing this code in C # for convenience for any C # encoder:

Here is my code (in ErrorHandler.cs):

 /// <summary> /// This class defines a global ErrorHandler, that allows us to control the fault message returned to the client and /// perform custom error processing like logging. /// </summary> public class ErrorHandler : IErrorHandler { private static readonly ILog Log = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType); /// <summary> /// Enables the creation of a custom <see cref="T:System.ServiceModel.FaultException`1" /> that is returned from an /// exception in the course of a service method. /// </summary> /// <remarks> /// This method is optionally used to transform standard exceptions into custom FaultException(Of TDetail) that /// can be passed back to the service client. /// </remarks> /// <param name="error">The <see cref="T:System.Exception" /> object thrown in the course of the service operation.</param> /// <param name="version">The SOAP version of the message.</param> /// <param name="fault"> /// The <see cref="T:System.ServiceModel.Channels.Message" /> object that is returned to the client, or /// service, in the duplex case. /// </param> public void ProvideFault(Exception error, MessageVersion version, ref Message fault) {} /// <summary> /// This method will be called whenever an exception occurs. Therefore, /// we log it and then return false so the error can continue to propagate up the chain. /// </summary> /// <param name="error">Exception being raised.</param> /// <returns>False to let the error propagate up the chain, or True to stop the error here.</returns> public bool HandleError(Exception error) { Log.Error(ex); //TODO your own logging return false; } 

Here is my code (in ErrorHandlerBehavior.cs):

 /// <summary> /// This class defines a BehaviorExtensionElement, so that we can use the ErrorServiceBehavior class, defined above, in /// our App.config. /// </summary> public class ErrorHandlerBehavior : BehaviorExtensionElement { /// <summary> /// Gets the type of behavior. /// </summary> public override Type BehaviorType { get { return typeof (ErrorServiceBehavior); } } /// <summary> /// Creates a behavior extension based on the current configuration settings. /// </summary> /// <returns> /// The behavior extension. /// </returns> protected override object CreateBehavior() { return new ErrorServiceBehavior(); } } 

Here is my code (in ErrorServiceBehavior.cs):

 /// <summary> /// This class defines a ServiceBehavior, that will allow us to add our custom ErrorHandler class, defined above, to /// each channel we have a service running on. /// </summary> public class ErrorServiceBehavior : IServiceBehavior { /// <summary> /// Provides the ability to inspect the service host and the service description to confirm that the service can run /// successfully. /// </summary> /// <param name="serviceDescription">The service description.</param> /// <param name="serviceHostBase">The service host that is currently being constructed.</param> public void Validate(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase) {} /// <summary> /// Provides the ability to pass custom data to binding elements to support the contract implementation. /// </summary> /// <param name="serviceDescription">The service description of the service.</param> /// <param name="serviceHostBase">The host of the service.</param> /// <param name="endpoints">The service endpoints.</param> /// <param name="bindingParameters">Custom objects to which binding elements have access.</param> public void AddBindingParameters(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase, Collection<ServiceEndpoint> endpoints, BindingParameterCollection bindingParameters) {} /// <summary> /// Provides the ability to change run-time property values or insert custom extension objects such as error handlers, /// message or parameter interceptors, security extensions, and other custom extension objects. /// </summary> /// <param name="serviceDescription">The service description.</param> /// <param name="serviceHostBase">The host that is currently being built.</param> public void ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase) { //Enumerate all channels and add the error handler to the collection var handler = new ErrorHandler(); foreach (ChannelDispatcher dispatcher in serviceHostBase.ChannelDispatchers) { dispatcher.ErrorHandlers.Add(handler); } } }