Wcf Error handling using IErrorHandler interface

Question

I have a question regarding WCF fault exceptions. I am implementing the IErrorHandler interface and creating a FaultException.

My question is this: When am I creating a FaultException, is there a pattern that I must follow to send a friendly error message to the client?

I log the actual exception using the HandleError method to the database and creating a FaultException in the ProvideFault method.

Given delow, there is my sample implementation of IErrorHandler interface.

public bool HandleError(Exception error)
{
    System.Diagnostics.Debug.WriteLine(error.Message);
            // Log the error to the Db  
    return true;
}

public void ProvideFault(Exception error, MessageVersion version, ref Message fault)
{
        // Here is a sample that I was playing with. 
    MessageFault faultException;
    if(error is DataException)
        faultException = new FaultException<string>(ErrorStrings.DatabaseOpenError, new FaultReason(ErrorStrings.DatabaseOpenError)).CreateMessageFault();
    else if (error is NullReferenceException)
        faultException = new FaultException<string>(ErrorStrings.NullDataError, new FaultReason(ErrorStrings.NullDataError)).CreateMessageFault();
    else
        faultException = new FaultException<string>(ErrorStrings.GeneralError, new FaultReason(ErrorStrings.GeneralError)).CreateMessageFault();

    fault = Message.CreateMessage(version, faultException, "");
}

I need some clarity on what exactly has to be done inside ProvideFault method to return a friendly Fault to the user. I am also planning to use localization to display errors. Not sure if this will be done by the client or if service should send localized messages.

Based on what I read, I should not send information of the stack from the error or EntityFramework errors, like EntityValidation errors and so on, to the client due to security reasons.

In this case, will I need to check for the type of exception and mine the details to be more appropriate before sending to the client?

Answer 1

The main requirement is to use the FaultContractAttribute so WCF understands the service contract being fulfilled. Please see http://msdn.microsoft.com/en-us/library/ms752208(v=vs.110).aspx

WCF will then also make sure your WSDL reflects your fault contracts.