IncludeExceptionDetailInFaults not behaving as thought

Question

I have this simple test project just to test the IncludeExceptionDetailInFaults behavior.

    public class Service1 : IService1
    {
        public string GetData(int value)
        {
            throw new InvalidCastException("test");
            return string.Format("You entered: {0}", value);
        }
    }

    [ServiceContract]
    public interface IService1
    {
        [OperationContract]
        string GetData(int value);
    }

In the app.config of the service i have it set to true

 <serviceDebug includeExceptionDetailInFaults="True" />

On the client side:

            try
            {
                using (var proxy = new ServiceReference1.Service1Client())
                    Console.WriteLine(proxy.GetData(5));
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }

This is what I thought the behavior was: Setting to includeExceptionDetailInFaults=true would propagate the exception detail to the client. But I'm always getting the CommunicationObjectFaultException.

I did try having the FaultContract(typeof(InvalidCastException)) on the contract but same behavior, only getting the CommunicationObjectFaultException.

The only way to make it work was to throw new FaultException(new InvalidCastException("test"));

But I thought with IncludeExceptionDetailInFaults=true the above was done automatically.

Am I missing something?

Answer 1

It's because you've put the service client inside a using block.

WCF clients are the one place in .NET where you shouldn't use using, because it will mask the "real" exception.

Technical explanation: Dispose calls Close, which will always throw a CommunicationObjectFaultedException if the channel is already faulted (i.e. as a result of a previous exception), which subsequently puts that exception at the top of the stack. When cleaning up an ICommunicationObject, in order to avoid masking the exception, you have to first check the State to see if it is faulted, and if so call Abort instead of Close.