Selecting XML nodes w/ namespace and XElement

[Michael Bray]

I'm playing around with XElement stuff, and I've come across a difficulty.
The XML document that I'm reading contains an xmlns declaration on the main
node...

<root xmlns="http://www.me.com">
<ANode>
<BNode>Hello</BNode>
<BNode>Goodby e</BNode>
</ANode>
</root>

I want to be able to query this document using XPath. I can successfully
do this with the following:

XmlDocument doc = new XmlDocument();
doc.LoadXml(s);
XmlNamespaceMan ager nsm = new XmlNamespaceMan ager(doc.NameTa ble);
nsm.AddNamespac e("t", "http://www.me.com");
int n = doc.SelectNodes ("/t:root/t:ANode/t:BNode", nsm).Count;

.... and I see that n = 2.

But when I try to convert this to XElement (and who knows I may be
WWWAAAYYY off here as I'm just starting to look at this):

XmlReader rdr = XmlReader.Creat e(new StringReader(s) );
XElement x = XElement.Load(r dr);
XmlNamespaceMan ager nsm = new XmlNamespaceMan ager(rdr.NameTa ble);
nsm.AddNamespac e("t", "http://www.me.com");
int n = x.XPathSelectEl ements("/t:root/t:ANode/t:BNode", nsm).Count();

.... I get n = 0.
What am I doing wrong?

-mdb

[Anthony Jones]

"Michael Bray" <mb***@dontemai lme.comwrote in message
news:Xn******** *********@207.4 6.248.16...

I'm playing around with XElement stuff, and I've come across a difficulty.
The XML document that I'm reading contains an xmlns declaration on the

main

node...

<root xmlns="http://www.me.com">
<ANode>
<BNode>Hello</BNode>
<BNode>Goodby e</BNode>
</ANode>
</root>

I want to be able to query this document using XPath. I can successfully
do this with the following:

XmlDocument doc = new XmlDocument();
doc.LoadXml(s);
XmlNamespaceMan ager nsm = new XmlNamespaceMan ager(doc.NameTa ble);
nsm.AddNamespac e("t", "http://www.me.com");
int n = doc.SelectNodes ("/t:root/t:ANode/t:BNode", nsm).Count;

... and I see that n = 2.

But when I try to convert this to XElement (and who knows I may be
WWWAAAYYY off here as I'm just starting to look at this):

XmlReader rdr = XmlReader.Creat e(new StringReader(s) );
XElement x = XElement.Load(r dr);
XmlNamespaceMan ager nsm = new XmlNamespaceMan ager(rdr.NameTa ble);
nsm.AddNamespac e("t", "http://www.me.com");
int n = x.XPathSelectEl ements("/t:root/t:ANode/t:BNode", nsm).Count();

... I get n = 0.
What am I doing wrong?

I've not done much with this new XElement either but I'd be willing to guess
that since x is root and in this case is the top most node (in the
XmlDocument the document is the top most node and root is a child). then
the path is wrong. / refers to root and root doesn't have a child called
root.

Try:-

"t:ANode/t:BNode"

I'm currently on a my 2000 machine so I can't test that at the moment.

--
Anthony Jones - MVP ASP/ASP.NET

[Chakravarthy]

Dude,

First, understand the difference between XMLDocument and XMLReader.
XMLDocument is inmemory .. where are XMLReader is not a cache.

thus, when you first queried you got the count, where are when you did the
second mechanism, it doesn't have loaded the entire XML into memory.

Hope am clear to you,


"Michael Bray" <mb***@dontemai lme.comwrote in message
news:Xn******** *********@207.4 6.248.16...

I'm playing around with XElement stuff, and I've come across a difficulty.
The XML document that I'm reading contains an xmlns declaration on the
main
node...

<root xmlns="http://www.me.com">
<ANode>
<BNode>Hello</BNode>
<BNode>Goodby e</BNode>
</ANode>
</root>

I want to be able to query this document using XPath. I can successfully
do this with the following:

XmlDocument doc = new XmlDocument();
doc.LoadXml(s);
XmlNamespaceMan ager nsm = new XmlNamespaceMan ager(doc.NameTa ble);
nsm.AddNamespac e("t", "http://www.me.com");
int n = doc.SelectNodes ("/t:root/t:ANode/t:BNode", nsm).Count;

... and I see that n = 2.

But when I try to convert this to XElement (and who knows I may be
WWWAAAYYY off here as I'm just starting to look at this):

XmlReader rdr = XmlReader.Creat e(new StringReader(s) );
XElement x = XElement.Load(r dr);
XmlNamespaceMan ager nsm = new XmlNamespaceMan ager(rdr.NameTa ble);
nsm.AddNamespac e("t", "http://www.me.com");
int n = x.XPathSelectEl ements("/t:root/t:ANode/t:BNode", nsm).Count();

... I get n = 0.
What am I doing wrong?

-mdb

[Jon Skeet [C# MVP]]

On Jul 10, 12:24*pm, "Chakravart hy" <dskch...@msn.c omwrote:

First, understand the difference between XMLDocument and XMLReader.
XMLDocument is inmemory .. where are XMLReader is not a cache.

thus, when you first queried you got the count, where are when you did the
second mechanism, it doesn't have loaded the entire XML into memory.

Doesn't XElement.Load(r dr) load the whole thing into memory though?
That's certainly what I'd expect.

Jon

[Pavel Minaev]

On Jul 10, 12:45*am, "Anthony Jones" <A...@yadayaday ada.comwrote:

"Michael Bray" <mb...@dontemai lme.comwrote in message

news:Xn******** *********@207.4 6.248.16...

I'm playing around with XElement stuff, and I've come across a difficulty.
The XML document that I'm reading contains an xmlns declaration on the

main

node...

<root xmlns="http://www.me.com">
* *<ANode>
* * * <BNode>Hello</BNode>
* * * <BNode>Goodby e</BNode>
* *</ANode>
</root>

I want to be able to query this document using XPath. *I can successfully
do this with the following:

XmlDocument doc = new XmlDocument();
doc.LoadXml(s);
XmlNamespaceMan ager nsm = new XmlNamespaceMan ager(doc.NameTa ble);
nsm.AddNamespac e("t", "http://www.me.com");
int n = doc.SelectNodes ("/t:root/t:ANode/t:BNode", nsm).Count;

... *and I see that n = 2.

But when I try to convert this to XElement (and who knows I may be
WWWAAAYYY off here as I'm just starting to look at this):

XmlReader rdr = XmlReader.Creat e(new StringReader(s) );
XElement x = XElement.Load(r dr);
XmlNamespaceMan ager nsm = new XmlNamespaceMan ager(rdr.NameTa ble);
nsm.AddNamespac e("t", "http://www.me.com");
int n = x.XPathSelectEl ements("/t:root/t:ANode/t:BNode", nsm).Count();

... *I get n = 0.

What am I doing wrong?

I've not done much with this new XElement either but I'd be willing to guess
that since x is root and in this case is the top most node (in the
XmlDocument the document is the top most node and root is a child). *then
the path is wrong. */ refers to root and root doesn't have a child called
root.

*Try:-

"t:ANode/t:BNode"

Yes, this is correct - "/" refers to the root node in the XML tree,
which is document in XmlDocument, but <rootelement in this case.
You may either follow the suggestion above, or load the XML into
System.Xml.Linq .XDocument instead - then you'll get the usual
behavior.

By the way, why XPath? The whole point of the new APIs is to use LINQ
queries instead:

XNamespace t = "http://www.me.com";
var result = doc.Elements(t + "ANode").Elemen ts(t + "BNode");

[Michael Bray]

Pavel Minaev <in****@gmail.c omwrote in news:ec4a9b96-77b8-4035-bbe3-
ac**********@k1 3g2000hse.googl egroups.com:

Yes, this is correct - "/" refers to the root node in the XML tree,
which is document in XmlDocument, but <rootelement in this case.
You may either follow the suggestion above, or load the XML into
System.Xml.Linq .XDocument instead - then you'll get the usual
behavior.

By the way, why XPath? The whole point of the new APIs is to use LINQ
queries instead:

XNamespace t = "http://www.me.com";
var result = doc.Elements(t + "ANode").Elemen ts(t + "BNode");

I'm using XPath because I want to be able to specify in a configuration
file which set of nodes to analyze. What you say makes a lot of sense if I
always know the path and can hard code it.

Even so, testing your code yields no results:

string s = "<root xmlns='http://www.me.com'><AN ode><BNode>Hell o</BNode>
<BNode>Goodby e</BNode></ANode></root>";

XDocument doc = XDocument.Parse (s);
XNamespace ns = "http://www.me.com";
int nn = doc.Elements(ns + "ANode").Elemen ts(ns + "BNode").Count( );

yields.. nn = 0. did I miss something?

-mdb

[Michael Bray]

"Anthony Jones" <An*@yadayadaya da.comwrote in
news:##******** ******@TK2MSFTN GP05.phx.gbl:

I've not done much with this new XElement either but I'd be willing to
guess that since x is root and in this case is the top most node (in
the XmlDocument the document is the top most node and root is a
child). then the path is wrong. / refers to root and root doesn't
have a child called root.

Try:-

"t:ANode/t:BNode"

Yup tried that before I posted (along with every other path I could think
of).. Same result - 0 nodes selected.

I'm just grasping at straws at this point - almost ready to abandon XML
Linq for now and stick with what works.

-mdb

[Martin Honnen]

Michael Bray wrote:

Even so, testing your code yields no results:

string s = "<root xmlns='http://www.me.com'><AN ode><BNode>Hell o</BNode>
<BNode>Goodby e</BNode></ANode></root>";

XDocument doc = XDocument.Parse (s);
XNamespace ns = "http://www.me.com";
int nn = doc.Elements(ns + "ANode").Elemen ts(ns + "BNode").Count( );

yields.. nn = 0. did I miss something?

Yes, certainly, the XDocument doc you construct has a root element named
'root' that your code ignores. You need/want
doc.Root.Elemen ts(ns + "ANode").Elemen ts(ns + "BNode").Count( )
or (naming the root explicitly)
doc.Element(ns + "root").Element s(ns + "ANode").Elemen ts(ns +
"BNode").Count( )

--

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

[Martin Honnen]

Michael Bray wrote:

"Anthony Jones" <An*@yadayadaya da.comwrote in
news:##******** ******@TK2MSFTN GP05.phx.gbl:

>I've not done much with this new XElement either but I'd be willing to
guess that since x is root and in this case is the top most node (in
the XmlDocument the document is the top most node and root is a
child). then the path is wrong. / refers to root and root doesn't
have a child called root.

Try:-

"t:ANode/t:BNode"

Yup tried that before I posted (along with every other path I could think
of).. Same result - 0 nodes selected.

Here is a working sample that outputs 2:

XElement root = XElement.Load(@ "..\..\XMLFile1 .xml");
XmlNamespaceMan ager mgr = new XmlNamespaceMan ager(new
NameTable());
mgr.AddNamespac e("pf", "http://www.me.com");

Console.WriteLi ne(root.XPathSe lectElements("p f:ANode/pf:BNode",
mgr).Count());

XML document is

<?xml version="1.0" encoding="utf-8" ?>
<root xmlns="http://www.me.com">
<ANode>
<BNode>Hello</BNode>
<BNode>Goodby e</BNode>
</ANode>
</root>

If your code does not find anything then please show us a complete
sample that demonstrates that, somewhere there must be a mistake.

--

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

[Michael Bray]

"Anthony Jones" <An*@yadayadaya da.comwrote in
news:##******** ******@TK2MSFTN GP05.phx.gbl:

I've not done much with this new XElement either but I'd be willing to
guess that since x is root and in this case is the top most node (in
the XmlDocument the document is the top most node and root is a
child). then the path is wrong. / refers to root and root doesn't
have a child called root.

Try:-

"t:ANode/t:BNode"

OK hmmm.. as I was playing around I think I fixed it... I can query
using both the XPath query mode and the Elements(..)... Here's the code
that works for me:

string s = "<root xmlns='http://www.me.com'><AN ode><BNode>Hell o</BNode>
<BNode>Goodby e</BNode></ANode></root>";

XmlReader rdr = XmlReader.Creat e(new StringReader(s) );
XDocument doc = XDocument.Load( rdr);
XmlNamespaceMan ager nsm = new XmlNamespaceMan ager(rdr.NameTa ble);
nsm.AddNamespac e("t", "http://www.me.com");
XNamespace ns = "http://www.me.com";

int n = doc.XPathSelect Elements("/t:root/t:ANode/t:BNode", nsm).Count();
int nn = doc.Elements(ns + "root").Element s(ns + "ANode").Elemen ts(ns +
"BNode").Count( );
int nnn = doc.Elements("r oot").Elements( "ANode").Elemen ts("BNode").Cou nt();

var q = doc.XPathSelect Elements("/t:root/t:ANode/t:BNode", nsm);
foreach (var v in q) Console.WriteLi ne(v.Value);
yields.... n = 2 nn = 2 nnn = 0
and outputs: Hello Goodbye

so I think the main thing that fixed it was loading into XDocument instead
of XElement. Also, when querying using the Elements() I needed to make
sure I added the XNamespace.

Thanks to everyone for their input... I knew it would be something simple
I was missing.

-mdb