selectNodes does not give node list when xmlns is used

Question

hello ,

I am trying to use IXMLDOMDocument's selectNodes method to get the node list based upon xpath expression.

I am passing the xpath expression in the method, but the node list returned is empty.

however if I remove the xmlns attribute from the root node then i get the correct number of nodes(which is 2) .

Here is my sample xml :

<?xml version="1.0" encoding="UTF-16"?>
<buttonViewer name="Code" setupPath="Applications.App1.Program1" loop="true" xmlns="buttonViewerSchema1_0">
 <buttonViewerSetup stepElapsedTime="0" controllerType="AC800M"/>
 <buttonStep stepName="S1" stepId="1" channel="1" initialStep="1">
  <ObjectPosition posX="1" posY="1"/>
 </buttonStep>
<buttonStep stepName="S2" stepId="2" channel="1" initialStep="1">
  <ObjectPosition posX="1" posY="2"/>
 </buttonStep>
</buttonViewer>

I am using the following code in VC++ (VS2005)

BSTR searchitem = NULL;
IXMLDOMNodeList *pNodes=NULL;
CComQIPtr<IXMLDOMDocument> pDOM(pDoc);
searchitem = SysAllocString(L"//buttonStep");
hr = pDOM->selectNodes(searchitem, &pNodes);
if (pNodes)
{
long length=0;
hr = pNodes->get_length(&length);
}

the length value is retuned as 0 after calling pNodes->get_length(), hr value is S_OK.

I can not change XML and also I am not sure about the use of  xmlns="buttonViewerSchema1_0"  as my application is not validating the xml against any xsd.

Answer 1

With XPath 1.0 you need to bind a prefix to that namespace URI and use that prefix in XPath expressions, with MSXML to bind a prefix you need to call the setProperty method of the document object with first argument "SelectionNamespaces" and second argument e.g. "xmlns:pf='buttonViewerSchema1_0'", then use an XPath expression alike "//pf:buttonStep".

Answer 2

Hello Martin,
Thanks for your reply. It worked.
Thanks again,

 

Answer 3

we just  encountered this problem too. the XPath expression worked fine in XMLSpy, but not in .NET

eg

XmlNodeList nodeList = doc.SelectNodes("//element");

the solution was as you say, add the namespace eg "http://yournamespace/" from the top of the xml doc to an XmlNamespaceManager

eg

XmlNamespaceManager namespaceManager = new XmlNamespaceManager(doc.NameTable);

namespaceManager.AddNamespace("pf", @"http://yournamespace/");

then to select the elements named "element"

eg

XmlNodeList nodeList = doc.SelectNodes("//pf:element", namespaceManager);

Perhaps MS could make this easier for developers, a 2 min job turned into a hour of searching Google.

Answer 4

Further to bamboowave's solution, you can use this to pick up the namespace dynamically so you don't have to hardcode it:

XmlNamespaceManager namespaceManager = new XmlNamespaceManager(doc.NameTable);

namespaceManager.AddNamespace("pf", doc.DocumentElement.NamespaceURI);

 

 

Answer 5

bamboowave wrote:

Perhaps MS could make this easier for developers, a 2 min job turned into a hour of searching Google.

 

+1. The "old" way should work as well. Wasted precious time.