Service parameter always null, but I can see it in the trace - wcf

Question

I'm having trouble implementing a service based off of a third-party wsdl. The third-party calls into my service and I can see the data in the trace, but my service parameters keep ending up null after deserialization.
As you can see from the trace, the alertXML node contains a XML document as a string. In the service code, this alertXML string is always null. Is there some special processing I need to do to handle this XML-as-a-string scenario?
Barring that, is there any way for me to just get a hold of the whole envelope so that I can parse the thing out?
Thanks
<E2ETraceEvent xmlns="http://schemas.microsoft.com/2004/06/E2ETraceEvent">
<System xmlns="http://schemas.microsoft.com/2004/06/windows/eventlog/system">
<EventID>0</EventID>
<Type>3</Type>
<SubType Name="Information">0</SubType>
<Level>8</Level>
<TimeCreated SystemTime="2011-07-08T17:46:14.7804786Z" />
<Source Name="System.ServiceModel.MessageLogging" />
<Correlation ActivityID="{54a3d088-5393-45a7-ae97-0bcd636f1750}" />
<Execution ProcessName="w3wp" ProcessID="3468" ThreadID="17" />
<Channel/>
<Computer>COMPUTER</Computer>
</System>
<ApplicationData>
<TraceData>
<DataItem>
<MessageLogTraceRecord Time="2011-07-08T13:46:14.7804786-04:00" Source="TransportReceive" Type="System.ServiceModel.Channels.BufferedMessage" xmlns="http://schemas.microsoft.com/2004/06/ServiceModel/Management/MessageTrace">
<HttpRequest>
<Method>POST</Method>
<QueryString></QueryString>
<WebHeaders>
<Content-Length>1807</Content-Length>
<Content-Type>text/xml; charset=utf-8</Content-Type>
<Expect>100-continue</Expect>
<Host>host</Host>
<User-Agent>Mozilla/4.0 (compatible; MSIE 6.0; MS Web Services Client Protocol 2.0.50727.3623)</User-Agent>
<SOAPAction>"http://www.xyz.com/wsdl/ProcessXML"</SOAPAction>
</WebHeaders>
</HttpRequest>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<soap:Body>
<ProcessXML xmlns="http://www.xyz.com/wsdl/">
<alertXml><?xml version="1.0" encoding="UTF-8"?><XMLOutgoing>MORE XML STRING</XMLOutgoing></alertXml>
</ProcessXML>
</soap:Body>
</soap:Envelope>
</MessageLogTraceRecord>
</DataItem>
</TraceData>
</ApplicationData>
EDIT:
The wsdl is:
<?xml version="1.0" encoding="UTF-8"?>
<wsdl:definitions xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns:tm="http://microsoft.com/wsdl/mime/textMatching/"
xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/"
xmlns:mime="http://schemas.xmlsoap.org/wsdl/mime/"
xmlns:tns="http://www.xyz.com/wsdl/"
xmlns:s="http://www.w3.org/2001/XMLSchema"
xmlns:soap12="http://schemas.xmlsoap.org/wsdl/soap12/"
xmlns:http="http://schemas.xmlsoap.org/wsdl/http/"
targetNamespace="http://www.xyz.com/wsdl/"
xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/">
<wsdl:types>
<s:schema elementFormDefault="qualified" targetNamespace="http://www.xyz.com/wsdl/">
<s:element name="ProcessXML">
<s:complexType>
<s:sequence>
<s:element minOccurs="0" maxOccurs="1" name="alertXml" type="s:string"/>
</s:sequence>
</s:complexType>
</s:element>
<s:element name="ProcessXMLResponse">
<s:complexType>
<s:sequence>
<s:element minOccurs="0" maxOccurs="1" name="ProcessXMLResult">
<s:complexType mixed="true">
<s:sequence>
<s:any/>
</s:sequence>
</s:complexType>
</s:element>
</s:sequence>
</s:complexType>
</s:element>
</s:schema>
</wsdl:types>
<wsdl:message name="ProcessXMLSoapIn">
<wsdl:part name="parameters" element="tns:ProcessXML"/>
</wsdl:message>
<wsdl:message name="ProcessXMLSoapOut">
<wsdl:part name="parameters" element="tns:ProcessXMLResponse"/>
</wsdl:message>
<wsdl:message name="ProcessXMLHttpGetIn">
<wsdl:part name="alertXml" type="s:string"/>
</wsdl:message>
<wsdl:message name="ProcessXMLHttpGetOut">
<wsdl:part name="Body"/>
</wsdl:message>
<wsdl:message name="ProcessXMLHttpPostIn">
<wsdl:part name="alertXml" type="s:string"/>
</wsdl:message>
<wsdl:message name="ProcessXMLHttpPostOut">
<wsdl:part name="Body"/>
</wsdl:message>
<wsdl:portType name="GenericServiceSoap">
<wsdl:operation name="ProcessXML">
<wsdl:input message="tns:ProcessXMLSoapIn"/>
<wsdl:output message="tns:ProcessXMLSoapOut"/>
</wsdl:operation>
</wsdl:portType>
<wsdl:portType name="GenericServiceHttpGet">
<wsdl:operation name="ProcessXML">
<wsdl:input message="tns:ProcessXMLHttpGetIn"/>
<wsdl:output message="tns:ProcessXMLHttpGetOut"/>
</wsdl:operation>
</wsdl:portType>
<wsdl:portType name="GenericServiceHttpPost">
<wsdl:operation name="ProcessXML">
<wsdl:input message="tns:ProcessXMLHttpPostIn"/>
<wsdl:output message="tns:ProcessXMLHttpPostOut"/>
</wsdl:operation>
</wsdl:portType>
<wsdl:binding name="GenericServiceSoap" type="tns:GenericServiceSoap">
<soap:binding transport="http://schemas.xmlsoap.org/soap/http"/>
<wsdl:operation name="ProcessXML">
<soap:operation soapAction="http://www.xyz.com/wsdl/ProcessXML" style="document"/>
<wsdl:input>
<soap:body use="literal"/>
</wsdl:input>
<wsdl:output>
<soap:body use="literal"/>
</wsdl:output>
</wsdl:operation>
</wsdl:binding>
<wsdl:binding name="GenericServiceSoap12" type="tns:GenericServiceSoap">
<soap12:binding transport="http://schemas.xmlsoap.org/soap/http"/>
<wsdl:operation name="ProcessXML">
<soap12:operation soapAction="http://www.xyz.com/wsdl/ProcessXML" style="document"/>
<wsdl:input>
<soap12:body use="literal"/>
</wsdl:input>
<wsdl:output>
<soap12:body use="literal"/>
</wsdl:output>
</wsdl:operation>
</wsdl:binding>
<wsdl:binding name="GenericServiceHttpGet" type="tns:GenericServiceHttpGet">
<http:binding verb="GET"/>
<wsdl:operation name="ProcessXML">
<http:operation location="/ProcessXML"/>
<wsdl:input>
<http:urlEncoded/>
</wsdl:input>
<wsdl:output>
<mime:content part="Body" type="text/xml"/>
</wsdl:output>
</wsdl:operation>
</wsdl:binding>
<wsdl:binding name="GenericServiceHttpPost" type="tns:GenericServiceHttpPost">
<http:binding verb="POST"/>
<wsdl:operation name="ProcessXML">
<http:operation location="/ProcessXML"/>
<wsdl:input>
<mime:content type="application/x-www-form-urlencoded"/>
</wsdl:input>
<wsdl:output>
<mime:content part="Body" type="text/xml"/>
</wsdl:output>
</wsdl:operation>
</wsdl:binding>
<wsdl:service name="GenericService">
</wsdl:service>
</wsdl:definitions>
The skeleton of the service code is:
Public Function ProcessXML(request As ProcessXMLRequest) As ProcessXMLResponse Implements GenericServiceSoap.ProcessXML
'request.Body is a non-null object but request.Body.alertXml is null
End Function

Answer 1

To send XML as a parameter or a property in a DataContract in WCF you need to use XmlElement for the .NET type of the parameter or property. Based on the WSDL in the question, the alertXml will be serialized as a string not XML by WCF. Here is what the WSDL for an XML operation parameter would look like:
<xs:element name="alertXml" nillable="true" minOccurs="0">
<xs:complexType>
<xs:sequence>
<xs:any minOccurs="0" processContents="lax"/>
</xs:sequence>
</xs:complexType>
</xs:element>
To see what all the WSDL should look like, implement a service like this:
[ServiceContract]
public interface IService1
{
[OperationContract]
string ProcessXml(XmlElement alertXml);
[OperationContract]
string ProcessSomeXml(ProcessXMLRequest xmlRequest);
}
[DataContract]
public class ProcessXMLRequest
{
public XmlElement someXml { get; set; }
}
//Service implementation
public class Service1 : IService1
{
public string ProcessXml(XmlElement alertXml)
{
XmlNode xmlToProcess = GetXmlToProcess(alertXml);
return string.Format("You entered: {0}", xmlToProcess.InnerText);
}
public string ProcessSomeXml(ProcessXMLRequest xmlRequest)
{
XmlNode xmlToProcess = GetXmlToProcess(xmlRequest.someXml);
return string.Format("You entered some: {0}", xmlToProcess.InnerText);
}
private XmlNode GetXmlToProcess(XmlElement alertXml)
{
var xmlToProcess = alertXml as XmlNode;
if (xmlToProcess == null)
{
var x = new XmlDocument();
x.LoadXml("<root>XML was null</root>");
xmlToProcess = x;
}
return xmlToProcess;
}
}