Null return on XmlDocument.SelectSingleNode through valid xpath

Question

I currently have the following code

nsmgr = new XmlNamespaceManager(xmlDoc.NameTable);
nsmgr.AddNamespace("soapenv", soapenv_namespace);
nsmgr.AddNamespace("de", de_namespace);

XmlNode xnEnvelope = xmlDoc.SelectSingleNode("//soapenv:Envelope", nsmgr);
XmlNode xnBody = xmlDoc.SelectSingleNode("//soapenv:Envelope/soapenv:Body", nsmgr);
XmlNode xnMessage = xnBody.SelectSingleNode("//soapenv:Envelope/soapenv:Body/message", nsmgr);

Which parses the following xml (truncated for readibility)

<?xml version="1.0" encoding="utf-8"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
     <soapenv:Body>
        <message     xmlns="http://www.origostandards.com/schema/ce/v2.1/CEBondSingleContractDetailResponse"     xmlns:ns2="http://www.origostandards.com/schema/ce/v2.1/CEBondSingleContractReferenceResponse" xmlns:ns3="http://www.origostandards.com/schema/ce/v2.1/CEBondSingleContractRequest" xmlns:ns4="http://www.origostandards.com/schema/tech/v1.0/SOAPFaultDetail">
        <de:m_content .....

Problem is the line XmlNode xnMessage = xnBody.SelectSingleNode("//soapenv:Envelope/soapenv:Body/message", nsmgr); returns null when i'd expect it to return the message element.

I highly suspect its to do with the blank namespace I have configured but I cant find the right combination of values to get it working.

Any pointers would be appreciated.

score 1 · Accepted Answer · answered Jul 22 '15 at 04:15

You have introduced default namespace here :

xmlns="http://www.origostandards.com/schema/ce/v2.1/CEBondSingleContractDetailResponse"

which causes message element and all of it's descendants without prefix to be recognized as in that default namespace (unless the descendant element has local default namespace). To access element in default namespace, simply register a prefix, for example d, and map it to the default namespace uri :

nsmgr.AddNamespace("d", "http://www.origostandards.com/schema/ce/v2.1/CEBondSingleContractDetailResponse");

Then use the newly registered prefix accordingly in the XPath expression :

XmlNode xnBody = xmlDoc.SelectSingleNode("//soapenv:Envelope/soapenv:Body", nsmgr);
XmlNode xnMessage = xnBody.SelectSingleNode("d:message", nsmgr);

This is a perfectly good answer too, and well commented, i upvoted this as you explain the solution more, and i think the answer is more in line with so post guidelines. — Ian Jowett, Jul 23 '15 at 09:13

score 1 · Answer 2 · answered Jul 22 '15 at 05:06

This is working

XmlDocument xmlDoc = new XmlDocument();
xmlDoc.Load(@"C:\Users\DummyUser\Desktop\Noname1.xml");

XmlNamespaceManager nsmgr = new XmlNamespaceManager(xmlDoc.NameTable);
nsmgr.AddNamespace("soapenv", "http://schemas.xmlsoap.org/soap/envelope/");
nsmgr.AddNamespace("de", "http://www.origostandards.com/schema/ce/v2.1/CEBondSingleContractDetailResponse");

XmlNode xnEnvelope = xmlDoc.SelectSingleNode("//soapenv:Envelope", nsmgr);
XmlNode xnBody = xnEnvelope.SelectSingleNode("//soapenv:Body", nsmgr);
XmlNode xnMessage = xnBody.SelectSingleNode("de:message", nsmgr);

and xml file is

<?xml version="1.0" encoding="utf-8"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
 <soapenv:Body>
    <message xmlns="http://www.origostandards.com/schema/ce/v2.1/CEBondSingleContractDetailResponse"     xmlns:ns2="http://www.origostandards.com/schema/ce/v2.1/CEBondSingleContractReferenceResponse" 
    xmlns:ns3="http://www.origostandards.com/schema/ce/v2.1/CEBondSingleContractRequest" 
    xmlns:ns4="http://www.origostandards.com/schema/tech/v1.0/SOAPFaultDetail">
    This is my sample message
    </message>
</soapenv:Body>
</soapenv:Envelope>

No way was it as simple as adding the DE namespace to the xml, thanks for this — Ian Jowett, Jul 23 '15 at 09:11

Null return on XmlDocument.SelectSingleNode through valid xpath

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