At a quick glance that looks OK. Why are you passing the XML as a string
instead of an XMLDocument?

Another thing to look at is to serialize your class: create an instance in
code, then serialize it, then look at the namespaces.

Perhaps the serialization class doesn't have the right namespace info?
xsd.exe /classes should generate it correctly.

There's an example of this in the upcoming book mentioned below.

--Matthew Blain
http://tips.serriform.com/
http://www.developingsolutionswithinfopath.com
I am attempting to build the following but running into problems.  The plan
is to have a user fill in a form and submit the form data to a webservice.
The webservice will then serialize the xml string submitted into a dataset
where it can then be saved more easily to the database.

I defined the dataset in a c# object and then converted the main datasource
in the infopath form to this dataset's XSD.  The form works fine, however
when I submit the data to my webservice, by business object responsible for
deserializing the XML form data into my dataset is balking at the namespace
prefixes inserted into the xml doc.  If I manually remove the namespace
prefixes from all my elements the xml form data deserializes without a
problem.

Here is what I have for my datasource XSD

<?xml version="1.0" encoding="utf-8" ?>
<xs:schema id="SamplingEvent"
targetNamespace=http://www.foobar.net/schemas/foobar
elementFormDefault="qualified" attributeFormDefault="qualified"
xmlns=http://www.foobar.net/schemas/foobar
xmlns:mstns="http://www.diadenver.net/schemas/es/SampleEvent"
xmlns:xs=http://www.w3.org/2001/XMLSchema
xmlns:msdata="urn:schemas-microsoft-com:xml-msdata"
xmlns:my=http://schemas.microsoft.com/office/infopath/2003/myXSD/2004-09-26T
22-51-25
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xd=http://schemas.microsoft.com/office/infopath/2003
xmlns:ns2="http://www.foobar.net/schemas/foobar"
xmlns:dfs=http://schemas.microsoft.com/office/infopath/2003/dataFormSolution
xmlns:s0="http://www.tempuri.org" xmlns:ns1=http://schemas.xmlsoap.org/wsdl/
xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/"
xmlns:soap=http://schemas.xmlsoap.org/wsdl/soap/
xmlns:http=http://schemas.xmlsoap.org/wsdl/http/
xmlns:mime="http://schemas.xmlsoap.org/wsdl/mime/"
xmlns:tm="http://microsoft.com/wsdl/mime/textMatching/">
<xs:element name="SamplingEvent" msdata:IsDataSet="true">
   <xs:complexType>
       <xs:sequence>
           <xs:element name="SampleEventType" minOccurs="0"
type="xs:string" maxOccurs="1" />
           ....

InfoPath Form Data
<?xml version="1.0" encoding="UTF-8"?><?mso-infoPathSolution
solutionVersion="1.0.0.53" productVersion="11.0.6357" PIVersion="1.0.0.0"
href="file:///C:\Data\Revision\DIA\Dev\ES\InfoPath\SWSampleCollection\bin\De
bug\SWSampleCollection.xsn"
name="urn:schemas-microsoft-com:office:infopath:DIA-Stormwater-Sample-Collec
tion-Form:http---www-foobar-net-schemas-foobar" language="en-us"
?><?mso-application progid="InfoPath.Document"?><ns2:SamplingEvent
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:dfs="http://schemas.microsoft.com/office/infopath/2003/dataFormSolutio
n" xmlns:s0="http://tempuri.org/"
xmlns:mime="http://schemas.xmlsoap.org/wsdl/mime/"
xmlns:tm="http://microsoft.com/wsdl/mime/textMatching/"
xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/"
xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns:http="http://schemas.xmlsoap.org/wsdl/http/"
xmlns:ns1="http://schemas.xmlsoap.org/wsdl/"
xmlns:ns2="http://www.foobar.net/schemas/foobar"
xmlns:msdata="urn:schemas-microsoft-com:xml-msdata"
xmlns:my="http://schemas.microsoft.com/office/infopath/2003/myXSD/2004-09-26
T22-51-25" xmlns:xd="http://schemas.microsoft.com/office/infopath/2003">
<ns2:SampleEventType>OTHER</ns2:SampleEventType>
....
Dataset Code
public void SubmitSampleCollection(string xmlSampleCollection)
{
   //Serialize the Xml Doc into a dataset to make it easier to work with.
   SamplingEvent dsSamplingEvent = new SamplingEvent();
   StringReader sr = new StringReader(xmlSampleCollection);
   XmlSerializer Xmls = new XmlSerializer(typeof(SamplingEvent));
   dsSamplingEvent = (SamplingEvent)Xmls.Deserialize(sr);        <-- line
of interest
}
It is the ns2: prefix that is screwing up my deserialization process.  If I
manually edit the Form's XML data by removing the ns2: prefix then I am able
to deserialize without a problem.
So...my questions are these
1) Am I able to write infopath's form data without namespaces (something
tells me no)?
2) How can I deserialize the xml into a dataset given the xml I'm getting in
the form?
TIA
-Jim