C# XML--SelectSingleNode/SelectNodes is failing.

gijomk · August 28th, 2006, 01:02 AM

I have one xml (which is HL7 format) as follows

----------------------------------

<?xml version="1.0" encoding="UTF-8"?>
<PORP_IN000001 xmlns="urn:hl7-org:v3" xmlns:mif="urn:hl7-org:v3/mif" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:hl7-org:v3
PORP_IN000001.xsd" ITSVersion="XML_1.0">
    <id/>
    <creationTime/>
    <interactionId/>
    <processingCode/>
    <processingModeCode/>
    <acceptAckCode/>
    <receiver>
        <device>
            <id/>
        </device>
    </receiver>
    <sender>
        <device>
            <id/>
        </device>
    </sender>
    <controlActProcess moodCode="EVN">
        <subject>
                 etc.................................
.......................
......
    </controlActProcess>
</PORP_IN000001>
----------------------------------

Please note that the above xml file is using the schema file "PORP_IN000001.xsd" and this file interally calls other schema files. There are 15 schema files using by this xml file. Only one schema file is directly refered in the xml file. All other schema files are called from the main schema file "PORP_IN000001.xsd"

I am trying to get the node from the xml file using c# code as follows

XmlDocument objXml=new XmlDocument();
objXml.Load(reader);
oNsMgr = new XmlNamespaceManager(objXml.NameTable);
oNsMgr.AddNamespace("", "urn:hl7-org:v3");
oNsMgr.AddNamespace("mif", "urn:hl7-org:v3/mif");
oNsMgr.AddNamespace("xsi", "http://www.w3.org/2001/XMLSchema-instance");
XmlNode Node=objXml.SelectSingleNode("//receiver");

But here objXml.SelectSingleNode("//receiver") is returning null value. Actully i have one node already present in the xml file.
Why the above query is failing. Can anybody help me?

Regards,

Gijo

joefawcett · August 28th, 2006, 03:18 AM

This is becoming the XSLT most FA of FAQs. See http://www.dpawson.co.uk/xsl/sect2/N5536.html especially numbers 13 and 23. You need to associate a prefix with the HL7 namespace and use that in your XPath statements.

Code:

oNsMgr.AddNamespace("hl7", "urn:hl7-org:v3");
XmlNode Node=objXml.SelectSingleNode("//hl7:receiver");
//or preferably
XmlNode Node=objXml.SelectSingleNode("/*/hl7:receiver");

It is nothing to do with the schema, just the way the namespaces are declared.

--

Joe (Microsoft MVP - XML)

mhkay · August 28th, 2006, 03:28 AM

In XPath 1.0 an unprefixed name always refers to a name that is in no namespace. To refer to a name in a namespace, you need to bind an explicit prefix.

I'm a little surprised that

oNsMgr.AddNamespace("", "urn:hl7-org:v3")

is allowed, since I don't see what meaning it can have.

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference