WCF service one-way method with fault message

Question

I wanted to create a one-way method for wcf service. Everything is ok unless I want to return fault message - if any.

I am using wscf blue code generator for wsdl and contract files.

In wsdl operation element I have only 'Input' and 'Fault' child elements. When I run the service i got the information that cannot declare fault message in one-way communication and .. one of the solutions is to set one-way to false .. what I did and well it works ok. If error occurs I get the message.

However I am wondering if I broke the web service/wsdl creation rules ... Because from wsdl service schema generator creates for me one-way communication (set to 'true') and other in other programming languages' generators would probably do the same ...

So Is it correct what i Did? How can I change wsdl so that the generator could create the code appropriately?

If in theory I cannot use fault in one-way communication then Do I need extra structure on response to return any error?

Thanks!

Enrico Campidoglio · Accepted Answer · 2012-03-13T09:27:29.290

It's true that one-way operations can't return faults to clients. If you want to generate a void not one-way service operation in WCF you will have to add an empty output element for that operation in your WSDL contract.

The .NET based WSDL parsers (such as WSCF.blue and svcutil) will generate one-way service operations for <wsdl:operation> elements that don't have a corresponding <wsdl:output> element.

For example this WSDL operation is one-way:

<wsdl:definitions>
    <wsdl:portType>
        ... 
        <wsdl:operation name="Foo">
           <wsdl:input message="tns:FooRequest" />
        </wsdl:operation>
    </wsdl:portType>
</wsdl:definitions>

On the other hand, defining an operation with an empty <wsdl:output> element (i.e an XSD type containing an empty sequence) will be mapped to a void not one-way method in .NET, which can optionally contain a fault declaration:

<wsdl:definitions>
    <wsdl:portType>
        ... 
        <wsdl:operation name="Foo">
           <wsdl:input message="tns:FooRequest" />
           <wsdl:output message="tns:FooResponse" />
           <wsdl:fault message="tns:FooFault" />
        </wsdl:operation>
    </wsdl:portType>
</wsdl:definitions>

where the <tns:FooResponse> type is simply defined as:

<xs:element name="FooResponse">
    <xs:complexType>
        <xs:sequence/>
    </xs:complexType>
</xs:element>

But the problem is, that if I define (in xsd) empty Response element and generate the wsdl, c# contract files etc, then it doesn't create void method but class with the response name. I just don't know how to force wscf blue to generate void non one-way service operation so that I could use fault messages.. Do you know ... ? — user740144, Mar 13 '12 at 09:24
Have a look at [this WSDL contract](http://codepaste.net/odijzx). This is generated by WCF out of a contract defined in code where the `Foo` operation is defined as `void Foo(FooRequest request)` decorated with `[OperationContract(OneWay = false)]`. The `FooResponse` type is defined as a complex type with an empty sequence. — Enrico Campidoglio, Mar 13 '12 at 09:44
When I did your way (creating empty output method (empty xsd element)) in result I got void method, and OneWay is not displayed at all, assuming now it is bidirectional communication. Thanks again for help — user740144, Mar 13 '12 at 10:09

score 1 · Answer 2 · answered Mar 13 '12 at 09:01

In WCF, one-way means operation has no returned values and the client does not care about the success or failure of the invocation.

In WCF, we also got some other operations which are naturally one-way, such as you operate MSMQ via WCF, then the operations are normally set to one-way.

So, If you want to return something to indicate the invocation status, then one-way is not a correct choice, you can just use the normal wcf operation which is not one-way instead.

For one-way operation, here is an article for your reference WCF ONE-WAY

score 0 · Answer 3 · answered Mar 13 '12 at 09:04

0

I feel you did correct thing. For any type of client (C#, JAVA, C++, PHP) they just need WSDL to create the proxy. I feel it should work in other languages as well. Best to use SoapUI (Neutral Soap client) to test your service.

answered Mar 13 '12 at 09:04

Shailesh

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WCF service one-way method with fault message

3 Answers3