Set namespaces in SOAP envelope for classes generated using svcutil - wcf

Question

We are working on a third party integration using WSDLs and XSDs that were provided to us. We've used svcutil to generate all the proxy classes for us which works fine. When we test with SoapUi everything works fine, however, when we try to send the response to our partner they're rejecting the SOAP message because the namespaces are being defined in the message header and body rather than the SOAP envelope.
Unfortunately, I can't make our partner change their process to accept our messages (even though I believe they are technically correct since we are defining the namespaces before we use them in the XML, just not where they expect them). I know I could put a message inspector in to massage the SOAP message before goes out, but I'd rather not go to that level of processing.
Are there any settings either for svcutil or even on the serialization attributes that we could set to have WCF output the namespaces on the envelope instead?
What they want:
<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/" xmlns:h="http://theirdomain.org/service">
<s:Header>
<h:myType>
<version>V1.0</version>
</h:myType>
</s:Header>
<s:Body>
<h:someElement />
</s:Body>
</s:Envelope>
What we're sending:
<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/" >
<s:Header>
<h:myType xmlns:h="http://theirdomain.org/service">
<version>V1.0</version>
</h:myType>
</s:Header>
<s:Body>
<h:someElement xmlns:h="http://theirdomain.org/service"/>
</s:Body>
</s:Envelope>

Answer 1

I think the right extensibility point for this may be a custom encoder (see http://msdn.microsoft.com/en-us/library/ms735115.aspx , or the samples at http://msdn.microsoft.com/en-us/library/ee960159.aspx , especially the first one). In the custom encoder, you would write the SOAP Envelope yourself (with the correct namespaces), and then call methods on the Message object to write out the headers and body (e.g. WriteBodyContents, see http://msdn.microsoft.com/en-us/library/ms734675.aspx - under "Writing Messages").