Is it possible to pull a single node (element) out of a complex XML
file, using SelectSingleNode(), and then deserialize that node to an
object?

Could someone please post, or point me to, a simple, but complete
example?

Yes, if your XML document looks like this, for example,

  <MyDocument>
     <ComplexInfo>
        <DontCare SomeStatistic="55" />
     </ComplexInfo>
     <MyObject>
        <Name>Geoff</Name>
     </MyObject>
  </MyDocument>

and you have a class to deserialize that looks like this,

  public class MyObject
  {
      public string Name;
  }

then you should have no problem selecting a single node, MyObject,
from the more complex document and then wrapping that node in an
XmlNodeReader to use for deserialization, like this,

  XmlSerializer serializer = new XmlSerializer( typeof( MyObject));
  XmlDocument doc = new XmlDocument( );
  doc.Load( "myDocument.xml");

  XmlNode node = doc.SelectSingleNode( "//MyObject");
  MyObject obj = serializer.Deserialize( new XmlNodeReader( node)) as MyObject;


Derek Harmon

Derek, thank you so much for the excellent response.  You are a
gentleman and a scholar.  You have confirmed for me that my approach
should work, but I'm still having trouble, I think because of
namespaces declared in the XML file.  Can you expand your example a
bit to account for a default namespace in the XML file?  Or, can you
tell me what might be wrong with my code, below?



The "deserialize" statement gives me the following error:

There is an error in the XML document. --> &lt;FIELDED_ADDRESS
xmlns='http://www.telcordia.com/IDN/ELMS6'&gt; was not expected.

"FIELDED_ADDRESS" is the name of the node I'm trying to
select/deserialize.

"http://www.telcordia.com/IDN/ELMS6" is a namespace declared in the
XML file.



My code looks like this:

XmlDocument ResponseDocument = new XmlDocument();
ResponseDocument.Load @"C:\MyFile.xml");
NamespaceManager = new
XmlNamespaceManager(ResponseDocument.NameTable);
NamespaceManager.AddNamespace("p",
"http://www.telcordia.com/IDN/ELMS6");
XPathQuery = @"//p:FIELDED_ADDRESS";
XmlNode AddressNode = ResponseDocument.SelectSingleNode(XPathQuery,
NamespaceManager);
if (AddressNode != null)
{
  ALTERNATIVE_ADDRESSFIELDED_ADDRESS FieldedAddress;
  XmlNodeReader NodeReader = new XmlNodeReader(AddressNode);
  XmlSerializer Serializer = new
XmlSerializer(typeof(ALTERNATIVE_ADDRESSFIELDED_ADDRESS),
"http://www.telcordia.com/IDN/ELMS6");
  FieldedAddress = Serializer.Deserialize(NodeReader) as
ALTERNATIVE_ADDRESSFIELDED_ADDRESS;
}



My XML file looks like this:

<?xml version="1.0" ?>
<Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
    <Object Id="pp">
        <ADDRESS_VALIDATION_OUTPUT
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://www.telcordia.com/IDN/ELMS6"
            version="ELMS6_ADDRESS_VALIDATION_OUTPUT_v2-0"
xsi:schemaLocation="http://www.telcordia.com/IDN/ELMS6
ADDRESS_VALIDATION_OUTPUT.xsd">
            <COMMON_QUERY_RSP></COMMON_QUERY_RSP>
            <ALTERNATIVE_ADDRESS_INFORMATION_LIST>
                <ALTERNATIVE_ADDRESS_INFORMATION>
                    <ALTERNATIVE_ADDRESS>
                        <FIELDED_ADDRESS>
                            <SANO>1445</SANO>
                            <SATH>DR</SATH>
                            <SASN>MONROE</SASN>
                            <SASS>NE</SASS>
                            <LD3>APT</LD3>
                            <LV3>C-27</LV3>
                            <CITY>ATLANTA</CITY>
                            <STATE>GA</STATE>
                        </FIELDED_ADDRESS>
                    </ALTERNATIVE_ADDRESS>
                </ALTERNATIVE_ADDRESS_INFORMATION>
            </ALTERNATIVE_ADDRESS_INFORMATION_LIST>
        </ADDRESS_VALIDATION_OUTPUT>
    </Object>
</Signature>

OK.  I got this working finally!  Cool.  Thank you.

The Serializer.Deserialize() method kept giving me "XXX was not
expected."

I thought it was talking about the namespace for XXX, but it was
actually complaining about the entire element.  Why?...  Apparently
because my class name didn't exactly match the element in the XML
file.

Unfortunately, my class name was generated from an XSD file for the
XML file I'm working with.  The class name has the form AAABBBCCC,
where the actual element I'm interested in, CCC, is nested under
elements AAA and BBB.  I really don't want to change it, to match the
element, because if the XSD changes in the future, I will use the
xsd.exe tool to regenerate the classes, and any manual changes I've
made will get blasted.

Maybe there is an option for xsd.exe to generate class names which
match the element names, or maybe there is a way to do the
Deserialize() without the names matching.  ???

I was able to use the XmlRoot attribute to map the class name to the
element name in the XML file, so at least now I won't have to actually
change the xsd.exe generated classes themselves.  Only issue now is
I'll have to add the attribute any time the XSD file changes.  Not
such a big deal.  Example below:


[System.Xml.Serialization.XmlTypeAttribute(Namespace="http://www.telcordia.com/IDN/ELMS6")]

[XmlRoot (ElementName="FIELDED_ADDRESS")]

public class ADDRESS_VALIDATION_OUTPUTALTERNATIVE_ADDRESS_INFORMATIONALTERNATIVE_ADDRESSFIELDED_ADDRESS

Thanks Derek.  Just curious if Deserializing the whole thing with
XmlSerializer to get the MyObject string and using that to deserialize the
string xml would be faster or slower?  Naturally you would need to define
MyDocument in a class first.  Does not XmlDocument deserializing the whole
thing also just to find the MyObject tag?  TIA

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