how do I use namespaces with XPathNavigator?

[Andy Fish]

Hi,

I can't figure out for the life of me how to select nodes using a namespace
in XpathNavigator. For example:

XPathDocument doc = new XPathDocument("file.xml");
XPathNavigator nav = doc.CreateNavigator();
XPathNodeIterator itr = nav.Select("/foo:bar");

Throws the exception "Namespace Manager or XsltContext needed. This query
has a prefix, variable, or user-defined function"

I notice that the Select() function of XmlDocument allows me to supply a an
XmlNamespaceManager object as a parameter, but neither XPathDocument or
XPathNavigator seem to have any such feature.

I'm happy to create an XmlNamespaceManager if someone could please explain
exactly where I should put it :)

Andy

[Oleg Tkachenko [MVP]]

Andy Fish wrote:

I can't figure out for the life of me how to select nodes using a namespace
in XpathNavigator. For example:

XPathDocument doc = new XPathDocument("file.xml");
XPathNavigator nav = doc.CreateNavigator();
XPathNodeIterator itr = nav.Select("/foo:bar");

Throws the exception "Namespace Manager or XsltContext needed. This query
has a prefix, variable, or user-defined function"

I notice that the Select() function of XmlDocument allows me to supply a an
XmlNamespaceManager object as a parameter, but neither XPathDocument or
XPathNavigator seem to have any such feature.

I'm happy to create an XmlNamespaceManager if someone could please explain
exactly where I should put it :)

In .NET 2.0 there is additional overload that accepts string expression
and IXmlNamespaceResolver (XmlNamespaceManager implements it) - see
http://msdn2.microsoft.com/en-us/library/6k4x060d.aspx.

In .NET 1.1 you have no choice but to compile XPathExpression manually:

XPathExpression expr = nav.Compile("book/@bk:ISBN");
XmlNamespaceManager mngr = new XmlNamespaceManager(new NameTable());
mngr.AddNamespace("bk","urn:samples");
expr.SetContext(mngr);
XPathNodeIterator ni = nav.Select(expr);

See
http://msdn.microsoft.com/library/de...lecttopic2.asp

--
Oleg Tkachenko [XML MVP, MCAD]
http://www.XmlLab.Net | http://www.XLinq.Net | http://blog.tkachenko.com

[Andy Fish]

>

In .NET 1.1 you have no choice but to compile XPathExpression manually:

XPathExpression expr = nav.Compile("book/@bk:ISBN");
XmlNamespaceManager mngr = new XmlNamespaceManager(new NameTable());
mngr.AddNamespace("bk","urn:samples");
expr.SetContext(mngr);
XPathNodeIterator ni = nav.Select(expr);

Thanks Oleg, it works a treat (but what a polaver though).

One small follow-up if I may. I would have thought that if I initialized the
namespace manager like this:

XmlNamespaceManager mngr = new XmlNamespaceManager(nav.NameTable);

then it would pick up the namespace prefixes from the document. However, it
doesn't (I still need to do the AddNamespace calls)

TIA

Andy

[Oleg Tkachenko [MVP]]

Andy Fish wrote:

One small follow-up if I may. I would have thought that if I initialized the
namespace manager like this:

XmlNamespaceManager mngr = new XmlNamespaceManager(nav.NameTable);

then it would pick up the namespace prefixes from the document. However, it
doesn't (I still need to do the AddNamespace calls)

No, first of all NameTable has nothing to do with namespaces - it's just
a collection of atomic strings (names) used to save memory and speed
up name comparisons. Second - there is no such thing as "prefixes from
the document" as in XML document namespace prefixes can be overriden and
undeclared in any order.

--
Oleg Tkachenko [XML MVP, MCAD]
http://www.XmlLab.Net | http://www.XLinq.Net | http://blog.tkachenko.com

[Martin Honnen]

Andy Fish wrote:

One small follow-up if I may. I would have thought that if I initialized the
namespace manager like this:

XmlNamespaceManager mngr = new XmlNamespaceManager(nav.NameTable);

then it would pick up the namespace prefixes from the document. However, it
doesn't (I still need to do the AddNamespace calls)

The NameTable is used to speed up string comparison, there is nothing
done like "picking up namespace prefixes".
As said, with .NET 2.0 you have some way to use the XPathNavigator
itself, once moved to the proper node you want to "pick up namespace
prefixes" from, itself as the namespace manager.
<http://groups.google.com/group/microsoft.public.dotnet.xml/msg/af7d7f9e2f422d7e?hl=en&>

--

Martin Honnen --- MVP XML
http://JavaScript.FAQTs.com/