sending XML message to webservice problem

[Chris]

I have a customer who wants to send us a XML message like this:

<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
<SOAP-ENV:Body>
<PurchaseOrder xmlns="http://tempuri.org/">
<OrderHeader>
<PONumber>10464</PONumber>
</OrderHeader>
<OrderDetails>
<ItemNumber>63434</ItemNumber>
<NumberOfItems>6</NumberOfItems>
</OrderDetails>
</PurchaseOrder>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>

This message can't be changed. So I build a webservice like this:

[WebMethod]
[SoapDocumentMethod(ParameterStyle=SoapParameterStyle.Bare)]
public string PurchaseOrder(XmlNode XmlPurchaseOrder)
{
//do something nice with XmlPurchaseOrder
}

When I am looking at the contents of XmlPurchaseOrder, I only see the
elements of the first node, OrderHeader. No Orderdetails. Basically, I
would retrieve in my function the whole XML message between the
PurchaseOrder tags, not only the first node. I tried several other
function calls, but I always ends up with the information of the first
node.

Anyone a clue?