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Handling exceptions thrown by WCF service

Exceptions thrown by the WCF services are represented as SOAP faults to the clients.Clients can handle these exceptions using a try and catch block. It is important to note that the services itself will continue running after throwing the exception. However, the exception will cause the client to fail if the exception is not handled by the client.

Further, when an exception occurs, the client may not see all the information related to the exception thrown. This is to ensure the security of the service. The amount of information depends on the type of the exception thrown. If it is a FaultException, lots of information about the exception is transmitted. However if it is not FaultException, just a generic fault information is sent to the client. In such situation, the faultcode in the SOAP message would be InternalServiceFault.

To include exception information, do one of the following:

  • Add the following annotation
                [ServiceBehavior(IncludeExceptionDetailInFaults=true)]

  • Add the following code to app.config

<system.serviceModel><behaviors><behavior name="default">
<serviceDebug includeExceptionDetailInFaults="true" />
 </behavior></behaviors></system.serviceModel>

Enabling Message Logging

To enable message logging use the following step:
  • Right click App.config of the host application
  • Select Edit WCF Configuration 
  • Select Diagnostics under Configuration
  • Click Enable MessageLogging
  • Click Message Logging under Diagnostics in Configuration
  • Set LogEntireMessage to True
To check the message you can use SvcTraceViewer, use the following steps:
  • Make your service throw an exception when one of the service operation is invoked
  • Run the application and make sure the an exception is thrown. 
  • Go to your host application folder. Now you should  be able to see a file called app_messages.svclog.
  • Double click on this file. It should open in SvcTraceViewer utility. 
  • Double click the first Activity. This should show you two MessageLogTrace. 
  • Notice that first message is a HttpRequest and the second message has a fault with faultcode InternalServiceFault.

Creating a FaultException

If you want to intentionally create a exception that is sent to the client then the best way to do this is to throw an exception of type FaultException or a type that derives from it.

throw new FaultException("An Error Occurred");

When a service throws a fault in this manner. This fault will be re-thrown as FaultException by the client.

You can also create a FaultException of type TDetails if you want the client to handle a contractually specified SOAP faults.

Order of handling exceptions in the client application 

  • FaultExceptions<TDetail>
  • FaultExceptions
  • ComminicationExceptions
  • TimeOutExceptions
  • Use finally block to check if the client channel has entered a faulted state if it has then the abort the client and create a new instance of the client if the client is required again. 

Links and references 

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