WCF Global Exception Handlers

in WCF if you handle an exception and convert it to a fault, this can travel thru the wire to the client. however you can not anticipate all exceptions that might be thrown by the service. In this case you may want to create a gloabl Exception handler that deals with any unhandled exception, convert it to a fault and send it through to the client.

The simple way to do this is by creating an attribute (ServiceExceptionHandlerAttribute) class and an error handler class (ServiceExceptionHandler) as follows

----------- the attribute --------------
using System.ServiceModel.Channels;
using System.ServiceModel.Description;


namespace Ayman.ExceptionHandling
{
public class ServiceExceptionHandlerAttribute : Attribute,IServiceBehavior
{
#region IServiceBehavior Members
public void AddBindingParameters(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase, System.Collections.ObjectModel.Collection endpoints, BindingParameterCollection bindingParameters)
{
}
public void ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
{
foreach (ChannelDispatcher dispatcher in serviceHostBase.ChannelDispatchers)
{
dispatcher.ErrorHandlers.Add(new ServiceExceptionHandler());
}
}
public void Validate(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
{
}
#endregion
}




------------ the error handler -----------------


using System.ServiceModel.Dispatcher;
using System.ServiceModel.Channels;



namespace Ayman.ExceptionHandling
{
public class ServiceExceptionHandler : IErrorHandler
{
public bool HandleError(Exception error)
{

return true;
}
public void ProvideFault(Exception error, MessageVersion version, ref Message fault)
{
ValidationFault validationFault = new ValidationFault();
FaultException fe = new FaultException(validationFault, error.Message);
MessageFault mf = fe.CreateMessageFault();
fault = Message.CreateMessage(version, mf, fe.Action);
}
}
}





And now all you need to do, is to decorate your service with this attribute as follows

using Ayman.ExceptionHandling;
namespace Ayman.MyService
{

[ServiceExceptionHandler]
public class MyService : IMyService
{

}
}