should I wrap all my WCF service code in a try catch block?

Question

try
{
    ///// here is the code that might throw erros. If I discover the user is unauthorized I throw a WebFaultException myself to alert the client
}      
catch (WebFaultException ex)
{
    throw ex; //but if I wrap all code in try-catch, I have to rethrow the exception o the status code reaches the client
}
catch (Exception ex)
{
    throw new WebFaultException(ex.Message, HttpStatusCode.InternalServerError);
}

Should I wrap all in a try-catch, or what do you recommend? I use WCF with rest-ful JSON services

Answer 1

you could do, but it would probably be better to implement IErrorHandler and add it as a behaviour to your service, which will allow your unhandled exceptions to be handled in a single place, so you'll be able to create a fault exception there to return details to the users.

ErrorHandler : IErrorHandler
{
... just implement the handling of errors here, however you want to handle them
}

then to create a behaviour which uses this:

/// <summary>
///   Custom WCF Behaviour for Service Level Exception handling.
/// </summary>
public class ErrorHandlerBehavior : IServiceBehavior
    {
    #region Implementation of IServiceBehavior


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


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


    public void ApplyDispatchBehavior (ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
        {
        IErrorHandler errorHandler = new ErrorHandler ();

        foreach (ChannelDispatcherBase channelDispatcherBase in serviceHostBase.ChannelDispatchers)
            {
            var channelDispatcher = channelDispatcherBase as ChannelDispatcher;

            if (channelDispatcher != null)
                {
                channelDispatcher.ErrorHandlers.Add (errorHandler);
                }
            }
        }

    #endregion
    }

Then if you are self hosting you can just add the behaviour programmatically:

 myServiceHost.Description.Behaviors.Add (new ErrorHandlerBehavior ());

if you want to add it via configuration then you need one of these:

public class ErrorHandlerElement : BehaviorExtensionElement
    {
    public override Type BehaviorType
        {
        get { return typeof (ErrorHandlerBehavior); }
        }

    protected override object CreateBehavior ()
        {
        return new ErrorHandlerBehavior ();
        }
    }
}

and then the configuration:

<system.serviceModel>
<extensions>
  <behaviorExtensions>
    <add name="ErrorLogging" type="ErrorHandlerBehavior, ErrorHandling, Version=1.0.0.0, Culture=neutral, PublicKeyToken=<whatever>" />
  </behaviorExtensions>
</extensions>
<bindings>
  <basicHttpBinding>
    <binding name="basicBinding">
    </binding>
  </basicHttpBinding>
</bindings>
<services>
  <service behaviorConfiguration="Service1Behavior" name="Service">
    <endpoint address="" binding="basicHttpBinding"  bindingConfiguration="basicBinding" contract="Service" />
  </service>
</services>
<behaviors>
  <serviceBehaviors>
    <behavior name="Service1Behavior">
      <serviceMetadata httpGetUrl="" httpGetEnabled="true" />
      <serviceDebug includeExceptionDetailInFaults="false" />
      <ErrorLogging />  <--this adds the behaviour to the service behaviours -->
    </behavior>
  </serviceBehaviors>
</behaviors>