How to use FaultException with details without specifying FaultContractAttribute - wcf

Question

I'm well aware of how to use FaultException with details. I know I can declare details contract, then I need to decorate the method which is expected to throw this kind of exceptions with [FaultContract(type(DetailsContractType))] and then I do throw FaultException in that method. All that is understood and worked. What I need is to be able to throw FaultException from all methods of all contracts in my WCF host. Adding [FaultContract(type(DetailsContractType))] to each method of each operation contract seems to much to me. Is there another way to allow this kind of exceptions without decorating methods with that attribute? If I just remove that attribute everything stops working and the exception becomes just FaultException on the client side. I was thinking about DataContractResolver but it looks like it is not involved in DetailsContractType resolution. Any ideas, hints, solutions?

Answer 1

Using IErrorHandler does not relieve you from decorating contract operations with the FaultContractAttribute what I'm trying to avoid. It is even stated in the example you referred, there is a comment there
// This behavior requires that the contract have a SOAP fault with a detail type of
GreetingFault.
and
throw new InvalidOperationException(String.Format(
"EnforceGreetingFaultBehavior requires a "
+ "FaultContractAttribute(typeof(GreetingFault)) in each operation contract. "
+ "The \"{0}\" operation contains no FaultContractAttribute.",
opDesc.Name)
);

Answer 2

You can implement the IErrorHandler interface to uniformly handle errors in WCF,here is a Demo:
[ServiceContract]
public interface IDemo {
[OperationContract]
void DeleteData(int dataId);
}
class DemoService : IDemo
{
public void DeleteData(int dataId)
{
if (dataId<0) {
throw new ArgumentException("error");
}
}
}
The above code is the interface and implementation class of WCF service.
class MyCustErrorHandler : IErrorHandler
{
public bool HandleError(Exception error)
{
return true;
}
public void ProvideFault(Exception error, MessageVersion version, ref Message fault)
{
FaultException faultException = new FaultException(error.Message);
MessageFault messageFault = faultException.CreateMessageFault();
fault = Message.CreateMessage(version,messageFault,"my-test-error");
}
}
The above code is the implementation class of the IErrorHandler interface.
class MyEndpointBehavior : IEndpointBehavior
{
public void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters)
{
return;
}
public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime)
{
return;
}
public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
{
MyCustErrorHandler handler = new MyCustErrorHandler();
endpointDispatcher.ChannelDispatcher.ErrorHandlers.Add(handler);
}
public void Validate(ServiceEndpoint endpoint)
{
return;
}
}
We add a custom error handling class by extending the Behavior method of the endpoint.
ServiceEndpoint ep = selfHost.AddServiceEndpoint(typeof(IDemo), new BasicHttpBinding(), "CalculatorService");
MyEndpointBehavior myEndpointBehavior = new MyEndpointBehavior();
ep.EndpointBehaviors.Add(myEndpointBehavior);
The client executes the following code will print "error" in the console:
try {
demoClient.DeleteData(-3);
}
catch (FaultException fault) {
string err = fault.Reason.GetMatchingTranslation().Text;
Console.WriteLine(err);
}
For more information about IErrorhandler,Please refer to the following link:
https://learn.microsoft.com/en-us/dotnet/api/system.servicemodel.dispatcher.ierrorhandler?view=netframework-4.8
UPDATE
If you don’t want to use IErrorhandler, you can also use FaultReason:
public string SayHello(string name) {
if (name.Length<2) {
FaultReasonText faultReasonText = new FaultReasonText("name length cannot be less than 2");
FaultReason reason = new FaultReason(faultReasonText);
throw new FaultException(reason);
}
return "hello";
}
The client needs to catch exceptions when calling:
try {
string res = channnel.Sayhello("B");
}
catch (FaultException fex) {
if (fex.Reason != null) {
FaultReason reason = fex.Reason;
//Get error information
FaultReasonText txt = reason.GetMatchingTranslation();
Console.WriteLine(txt.Text);
}
}