Question

When throwing a FaultException<CustomFault> like this:

throw new FaultException<CustomFault>(new CustomFault("Custom fault message"));

I get the following: “The creator of this fault did not specify a Reason.”
Now according to this MSDN article one isn’t required to use the FaultReason

I have the following Service Contract:

[OperationContract]
[FaultContract(typeof(CustomFault))]
CustomType[] SomeMethod(int someParameter);

[DataContract]
public class CustomFault
{
    private string report;

    public CustomFault(string message)
    {
        this.report = message;
    }

    [DataMember]
    public string Message
    {
        get { return this.report; }
        set { this.report = value; }
    }
}

There is a comment on the MSDN article that suggest it is mandatory to use the other FaultReason, but in several other places I have seen people arguing that you shouldn’t use the FaultReason unless necessary.

So my question is as follows; is it really mandatory to use the FaultReason and if not – how can i prevent the exception raised when trying to throw a FaultException?

EDIT

By running the sample project from this article I get the excact same behavior. Maybe it’s caused by an update in .NET an the documentation/samples not being updated.

Answer 1

The fault reason is required while the details are optional.

WCF uses the value of the FaultException.Reason property to populate the <faultstring> element of the SOAP Fault, which is required by the SOAP specification:

faultstring
The faultstring element is intended to provide a human readable explanation of the fault and is not intended for algorithmic
processing. […] It MUST be present in a SOAP Fault element and
SHOULD provide at least some information explaining the nature of the
fault.

Hence, you must provide a reason for the fault when throwing a FaultException from a WCF service.