Proper way to throw exception over WCF

Question

I'm trying to send exceptions over WCF in the most generic way possible. Here's what I've got:

[ServiceContract]
interface IContract
{
    [OperationContract]
    void Foo();
}

class ContractImplementation: IContract
{
    public void Foo()
    {
        try
        {
            Bar();
        }
        catch (Exception ex)
        {
            throw new FaultException<Exception>(ex, ex.Message);
        }
    }
}

The exception that is actually coming out of Bar is:

[Serializable]
class MyException : Exception
{
    // serialization constructors
}

The error I'm seeing in the server-side WCF logging is:

Type 'MyException' with data contract name 'MyException:http://schemas.datacontract.org/2004/07/MyException' 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.

What I've tried so far:

[ServiceKnownType(typeof(MyException))]
[ServiceContract]
interface IContract
{
    [FaultContract(typeof(MyException))]
    [OperationContract]
    void Foo();
}

But no luck.

Could it be because you throw new FaultException<Exception>(ex, ex.Message); and not "throw new FaultException<MyException>(ex, ex.Message);" ? Also, the TDetail of FaultException should not necessary be an exception — hazzik
@hazzik: I'm putting the actual exception in the Detail because I want to rethrow it on the client side. — Tudor

Ricardo Pontual Ricardo Pontual · Accepted Answer · 2015-06-30T17:54:49

First, in MyException, remove the inheritance from Exception and make it public.

Second, when you declare your service contract, declare exception as it follows:

[FaultContractAttribute(
        typeof(MyException),
        Action = "", 
        Name = "MyException", 
        Namespace = "YourNamespace")]
    [System.ServiceModel.XmlSerializerFormatAttribute(SupportFaults = true)]
    [OperationContract]
    void Foo()

Finally, you can throw your Exception like this:

throw new FaultException<MyException>
             (
                 new MyException(ex.Message),
                 new FaultReason("Description of your Fault")

             );

Hope it helps.

Proper way to throw exception over WCF

2 Answers