WCF throwing CommunicationException when FaultException is thrown - wcf

Question

Solution:
A bit of tracing showed the CommunicationException was being thrown because there was an issue with my exception T not serializing correctly; because, two layers deep, I had an anonymously typed object, which was unserializable. Removing it and bubbling up the changes appeared to fix it. There was somethinge else small I did before that, but I can't remember for the life of me what it was, only that it wasn't done in the config.
I was getting messages from my traces such as:
Type 'RebuiltWCFService.Requests.HelloWorldRequest' with data contract name 'HelloWorldRequest:http://schemas.datacontract.org/2004/07/RebuiltWCFService.Requests' is not expected.
Consider using a DataContractResolver or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer.
Original post
I've encountered a seemingly strange issue today that I just cant't find an answer to!
The problem: my service is throwing a CommunicationException when I throw a FaultException! It does not do this if I don't throw an exception.
In my service, I'm properly defining the fault contracts:
[OperationContract]
[FaultContract(typeof(Faults.HelloWorldFault))]
Responses.HelloWorldResponse HelloWorld(Requests.HelloWorldRequest parameter);
Then under error conditions I'm throwing an exception of the correct type:
if (_errors.Count() > 0)
{
Faults.HelloWorldFault fault = new Faults.HelloWorldFault(_errors);
throw new FaultException<Faults.HelloWorldFault>(fault, new FaultReason("There are one or more errors in the request. Check the 'Errors' property for more detaisl"));
}
And then I'm catching it on the client end:
try
{
response = client.HelloWorld(new BasicService.HelloWorldRequest() { Number = 49 });
client.Close();
Console.WriteLine(String.Format("Response message: {0}, Response number: {1}", response.Message, response.Number));
}
catch (FaultException<BasicService.HelloWorldFault> ex)
{
...
}
That all seems OK to me, and like it should work. However, as soon as I go to test my error clauses (by providing bad data, such as a missing field), the whole thing dies on me. When I throw my FaultException, the service instead throws a CommunicationException with the message
An error occurred while receiving the HTTP response to http://localhost:8732/Design_Time_Addresses/RebuiltWCFService/Service1/.
This could be due to the service endpoint binding not using the HTTP protocol.
This could also be due to an HTTP request context being aborted by the server (possibly due to the service shutting down).
See server logs for more details.
Can anybody offer some insight on this one? I am using the basicHttp binding, and I've also tried it with wsHttp. I will post my config file upon request.

Answer 1

A FaultException is a child of CommunicationException. So there is nothing wrong in what's happening in your code.
If you are uncertain about what the exception is while handling, it is usually reported as CommunicationException. If you want to handle your specific exception in your own way, use the following structure.
try
{ ... }
catch (FaultException<MyDemoException> me)
{ ... }
catch (FaultException fe)
{ ... }
catch (CommunicationException ce)
{ ... }
catch (Exception ex)
{ ... }
In the above structure, Exception is parent of CommunicationException. CommunicationException is the parent of FaultException and so on.
System.Object
System.Exception
System.SystemException
System.ServiceModel.CommunicationException
System.ServiceModel.FaultException
System.ServiceModel.FaultException<TDetail>
System.ServiceModel.Web.WebFaultException<T>

Answer 2

Thanks guys, you helped me to understand the issue in a better way. My observation: I kept a List MyData - to hold any generic/dynamic collection, that was unable to serialize, so resulting to close the connection, so the communication exception.
When I removed the List from Fault Contract, and throw Fault style, it was clearly giving Fault contract exception, instead of communication exception.
Hope it helps,
HydTechie.

Answer 3

I ran into this problem because I had one or more breakpoints in the wrong place. I removed all breakpoints with Debug..Delete all Breakpoints (Ctrl-Alt-F9), and all of the CommunicationException exceptions disappeared and were replaced with the correct messages coming back.
Yes, the timeout is 60 seconds, so this never should have occurred, so it was probably some weird artifact of Visual Studio 2012.