XmlDocument.Sel ectSingleNode() & namespaces - doesn't work

[David Thielen]

Hi;

If there are no namespaces this works fine for me. But if the xml has
namespaces, then I get either no node back or an exception.

Here is the sample xml:
<root xmlns="http://www.test.org"
xmlns:sns="http ://www.test.org/sub"
xmlns:mns="http ://www.test.org/mini">
<data>
<items>
<item id="1">
<sns:subItem sid="11">dave</sns:subItem>
<sns:subItem sid="12">thiele n</sns:subItem>
</item>
<item id="2">
<sns:subItem sid="21">shirle y</sns:subItem>
</item>
</items>
<mns:more>dav e thielen</mns:more>
</data>
</root>

1. If I do SelectSingleNod e("/root/data/items/item/@id") - I get no nodes
returned. This is the case if I create an XmlNamespaceMan ager or not.

2. If I do SelectSingleNod e("/root/data/items/item/sns:subItem/@sid") where
I have a namespace qualified node I get:

2a. If there is no XmlNamespaceMan ager I get an exception.

2b. If I add the following code:
XmlNamespaceMan ager context = new XmlNamespaceMan ager(doc.NameTa ble);
context.AddName space("sns", "http://www.test.org/sub");
node = doc.SelectSingl eNode(("/root/data/items/item/sns:subItem/@sid",
context);
Then I get no nodes returned (but at least no exception is thrown).

I tested all of the in XmlSpy and the xpath works there as expected.

So what is going on?

First off, even if I add the namespaces, I still can't get any node
returned. Both those with namespaces and those without evaluate to no nodes.

Second, why does it throw an exception if I don't create a namespace
manager? The namespaces exist in the xml file and by definition, those
mappings should be used. Also, to quote from
http://msdn.microsoft.com/library/de...edprefixes.asp
"If the msbooks namespace was not added to the XmlNamespaceMan ager, and if it
is not in the name table of the document, then an exception is thrown." So
there should be no exception thrown for namespaces that are defined in the
document.

Help please - this makes no sense to me.

--
thanks - dave

[Kevin Yu [MSFT]]

Hi Dave,

First of all, I would like to confirm my understanding of your issue. From
your description, I understand that you are trying to use SelectSingleNod e
to get the attribute. If there is any misunderstandin g, please feel free to
let me know.

Since the nodes are under the default namespace, SelectSingleNod e require
us to specify the namespace for each node in the Xpath expression including
the default namespace. You can get /root/data/items/item/@id with the
following piece of code.

XmlDocument doc =new XmlDocument();
doc.LoadXml(s);
XmlNamespaceMan ager nsmgr = new XmlNamespaceMan ager(doc.NameTa ble);
nsmgr.AddNamesp ace("d", "http://www.test.org");
nsmgr.AddNamesp ace("sns", "http://www.test.org/sub");
nsmgr.AddNamesp ace("mns", "http://www.test.org/mini");
XmlNode node = doc.SelectSingl eNode("//d:root/d:data/d:items/d:item/@id",
nsmgr);

Also, to get to /root/data/items/item/sns:subItem/@sid, Please use the
following code.

XmlNode node =
doc.SelectSingl eNode("//d:root/d:data/d:items/d:item/sns:subItem/@sid",
nsmgr);

HTH.

Kevin Yu
=======
"This posting is provided "AS IS" with no warranties, and confers no
rights."

[David Thielen]

Hello;

My problem is that I am not hardcoding the xpath - I have to accept what the
user types in. And I have to accept any legal xpath and it is legal to enter
it with no namespace on the nodes that are in the default namespace.

How can I get this to handle any legal xpath string? (In other words, to
work the same way XmlSpy, dom4j, XSLT, and every other program that accepts
xpath works.)

--
thanks - dave
"Kevin Yu [MSFT]" wrote:

Hi Dave,

First of all, I would like to confirm my understanding of your issue. From
your description, I understand that you are trying to use SelectSingleNod e
to get the attribute. If there is any misunderstandin g, please feel free to
let me know.

Since the nodes are under the default namespace, SelectSingleNod e require
us to specify the namespace for each node in the Xpath expression including
the default namespace. You can get /root/data/items/item/@id with the
following piece of code.

XmlDocument doc =new XmlDocument();
doc.LoadXml(s);
XmlNamespaceMan ager nsmgr = new XmlNamespaceMan ager(doc.NameTa ble);
nsmgr.AddNamesp ace("d", "http://www.test.org");
nsmgr.AddNamesp ace("sns", "http://www.test.org/sub");
nsmgr.AddNamesp ace("mns", "http://www.test.org/mini");
XmlNode node = doc.SelectSingl eNode("//d:root/d:data/d:items/d:item/@id",
nsmgr);

Also, to get to /root/data/items/item/sns:subItem/@sid, Please use the
following code.

XmlNode node =
doc.SelectSingl eNode("//d:root/d:data/d:items/d:item/sns:subItem/@sid",
nsmgr);

HTH.

Kevin Yu
=======
"This posting is provided "AS IS" with no warranties, and confers no
rights."

[Harry_Crow]

try out SelectSingleNod e("//root/data/items/item[@id='1']")
SelectSingleNod e("//root/data/items/item[@id='2']")

Harry

"David Thielen" wrote:

Hi;

If there are no namespaces this works fine for me. But if the xml has
namespaces, then I get either no node back or an exception.

Here is the sample xml:
<root xmlns="http://www.test.org"
xmlns:sns="http ://www.test.org/sub"
xmlns:mns="http ://www.test.org/mini">
<data>
<items>
<item id="1">
<sns:subItem sid="11">dave</sns:subItem>
<sns:subItem sid="12">thiele n</sns:subItem>
</item>
<item id="2">
<sns:subItem sid="21">shirle y</sns:subItem>
</item>
</items>
<mns:more>dav e thielen</mns:more>
</data>
</root>

1. If I do SelectSingleNod e("/root/data/items/item/@id") - I get no nodes
returned. This is the case if I create an XmlNamespaceMan ager or not.

2. If I do SelectSingleNod e("/root/data/items/item/sns:subItem/@sid") where
I have a namespace qualified node I get:

2a. If there is no XmlNamespaceMan ager I get an exception.

2b. If I add the following code:
XmlNamespaceMan ager context = new XmlNamespaceMan ager(doc.NameTa ble);
context.AddName space("sns", "http://www.test.org/sub");
node = doc.SelectSingl eNode(("/root/data/items/item/sns:subItem/@sid",
context);
Then I get no nodes returned (but at least no exception is thrown).

I tested all of the in XmlSpy and the xpath works there as expected.

So what is going on?

First off, even if I add the namespaces, I still can't get any node
returned. Both those with namespaces and those without evaluate to no nodes.

Second, why does it throw an exception if I don't create a namespace
manager? The namespaces exist in the xml file and by definition, those
mappings should be used. Also, to quote from
http://msdn.microsoft.com/library/de...edprefixes.asp
"If the msbooks namespace was not added to the XmlNamespaceMan ager, and if it
is not in the name table of the document, then an exception is thrown." So
there should be no exception thrown for namespaces that are defined in the
document.

Help please - this makes no sense to me.

--
thanks - dave

[Martin Honnen]

David Thielen wrote:

My problem is that I am not hardcoding the xpath - I have to accept what the
user types in. And I have to accept any legal xpath and it is legal to enter
it with no namespace on the nodes that are in the default namespace.

While an XPath expression
element-name
is syntactically correct it always selects only elements with the
element name 'element-name' in no namespace, if you want to select
elements in a namespace then you need to bind a prefix to the namespace
URI and use that prefix in the XPath expression, no change to the XML
document is needed for that, see also
<http://www.faqts.com/knowledge_base/view.phtml/aid/34022/fid/616>

--

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

[David Thielen]

Hi;

Tried - it didn't work.

--
thanks - dave
"Harry_Crow " wrote:

try out SelectSingleNod e("//root/data/items/item[@id='1']")
SelectSingleNod e("//root/data/items/item[@id='2']")

Harry

"David Thielen" wrote:

Hi;

If there are no namespaces this works fine for me. But if the xml has
namespaces, then I get either no node back or an exception.

Here is the sample xml:
<root xmlns="http://www.test.org"
xmlns:sns="http ://www.test.org/sub"
xmlns:mns="http ://www.test.org/mini">
<data>
<items>
<item id="1">
<sns:subItem sid="11">dave</sns:subItem>
<sns:subItem sid="12">thiele n</sns:subItem>
</item>
<item id="2">
<sns:subItem sid="21">shirle y</sns:subItem>
</item>
</items>
<mns:more>dav e thielen</mns:more>
</data>
</root>

1. If I do SelectSingleNod e("/root/data/items/item/@id") - I get no nodes
returned. This is the case if I create an XmlNamespaceMan ager or not.

2. If I do SelectSingleNod e("/root/data/items/item/sns:subItem/@sid") where
I have a namespace qualified node I get:

2a. If there is no XmlNamespaceMan ager I get an exception.

2b. If I add the following code:
XmlNamespaceMan ager context = new XmlNamespaceMan ager(doc.NameTa ble);
context.AddName space("sns", "http://www.test.org/sub");
node = doc.SelectSingl eNode(("/root/data/items/item/sns:subItem/@sid",
context);
Then I get no nodes returned (but at least no exception is thrown).

I tested all of the in XmlSpy and the xpath works there as expected.

So what is going on?

First off, even if I add the namespaces, I still can't get any node
returned. Both those with namespaces and those without evaluate to no nodes.

Second, why does it throw an exception if I don't create a namespace
manager? The namespaces exist in the xml file and by definition, those
mappings should be used. Also, to quote from
http://msdn.microsoft.com/library/de...edprefixes.asp
"If the msbooks namespace was not added to the XmlNamespaceMan ager, and if it
is not in the name table of the document, then an exception is thrown." So
there should be no exception thrown for namespaces that are defined in the
document.

Help please - this makes no sense to me.

--
thanks - dave

[David Thielen]

Hi;

There are a couple of things that don't strike me as right about this.

First, these xpath queries do work in XmlSpy and when using dom4j. And I
understand the difference between no namespace and default namespace - but
the 1.0 spec is a bit unclear on exactly what this means in practice. But it
seems to me that this should work in .NET since it works elsewhere.

Second, the namespaces are defined in the xml file. So why do they need to
be set again using XmlNamespaceMan ager.AddNamespa ce()? It should be able to
get those when parsing the xml file.

In my case I can't force these things because I have to handle xml files and
xpath statements given to me by a user in my app. So I can't create a
hard-coded work-around for this.

???

--
thanks - dave
"Martin Honnen" wrote:

David Thielen wrote:

My problem is that I am not hardcoding the xpath - I have to accept what the
user types in. And I have to accept any legal xpath and it is legal to enter
it with no namespace on the nodes that are in the default namespace.

While an XPath expression
element-name
is syntactically correct it always selects only elements with the
element name 'element-name' in no namespace, if you want to select
elements in a namespace then you need to bind a prefix to the namespace
URI and use that prefix in the XPath expression, no change to the XML
document is needed for that, see also
<http://www.faqts.com/knowledge_base/view.phtml/aid/34022/fid/616>

--

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

[Kevin Yu [MSFT]]

Hi Dave,

I'm afraid this is by design in .NET framework. The XmlSpy uses a standard
way in the spec, but in the .NET Xml, we have its own implementation of the
Xpath query.

The XmlNamespaceMan ager object is designed to serve as a collection of
namespace definitions. It is used by the .NET Framework XML processors to
resolve and manage the scope of namespaces used in XML documents. So you
must use a System.Xml.XmlN amespaceManager object to provide the required
namespace resolution and scope management support.

You can check the following KB articles for more information.

http://support.microsoft.com/?id=313828
http://support.microsoft.com/?id=316913

Kevin Yu
=======
"This posting is provided "AS IS" with no warranties, and confers no
rights."

[David Thielen]

Hi;

Ok - this seems to be required. But it's nuts - this does not match the W3C
standard as far as I can tell. Especially ignoring the namespace settings in
the xml file.

Does anyone have any code to work around this? There have to be others who
have parsed the xml file to pull out the namespace declarations and declare
them programatically to get the standard xpath functionality.

--
thanks - dave
"Kevin Yu [MSFT]" wrote:

Hi Dave,

I'm afraid this is by design in .NET framework. The XmlSpy uses a standard
way in the spec, but in the .NET Xml, we have its own implementation of the
Xpath query.

The XmlNamespaceMan ager object is designed to serve as a collection of
namespace definitions. It is used by the .NET Framework XML processors to
resolve and manage the scope of namespaces used in XML documents. So you
must use a System.Xml.XmlN amespaceManager object to provide the required
namespace resolution and scope management support.

You can check the following KB articles for more information.

http://support.microsoft.com/?id=313828
http://support.microsoft.com/?id=316913

Kevin Yu
=======
"This posting is provided "AS IS" with no warranties, and confers no
rights."

[Oleg Tkachenko [MVP]]

David Thielen wrote:

First, these xpath queries do work in XmlSpy and when using dom4j.
That means XmlSpy and Dom4J are seriously broken. Your queries must
return nothing on your XML as per XPath 1.0 spec.
And I
understand the difference between no namespace and default namespace - but
the 1.0 spec is a bit unclear on exactly what this means in practice. But it
seems to me that this should work in .NET since it works elsewhere.
It doesn't work with any conformant XSLT processor I'm aware. Actually
it works as expected - returns nothing. That's the most FAQ ever with
XPath. Read "XML Namespaces and How They Affect XPath and XSLT" at
http://msdn.microsoft.com/library/de...ml05202002.asp

Second, the namespaces are defined in the xml file. So why do they need to
be set again using XmlNamespaceMan ager.AddNamespa ce()? It should be able to
get those when parsing the xml file.
Because in XML you might define zillion of different namespaces with or
without clashing prefixes and so when you query for an element you must
say explicitly which namespace you are interested in. Take a look at
this XML:
<foo xmlns="urn:bar" >
<foo xmlns="urn:foo"/>
</foo>

Which foo element should be selected by "//foo" query? The answer as per
XPath 1.0 spec is - none, because "foo" in XPath 1.0 means element in no
namespace.
In my case I can't force these things because I have to handle xml files and
xpath statements given to me by a user in my app. So I can't create a
hard-coded work-around for this.

Then your app is broken by design. When user query XML she must be able
to define mapping between namespace prefixes used in a query and
namespace URIs.

--
Oleg Tkachenko [XML MVP, MCAD]
http://blog.tkachenko.com