Why XPath expression doesn't return any results in C# but it does outside C#?

Question

I'm working on Open XML document format for excel sheets.

var nodeList = WorksheetXml.SelectNodes(@"//c[child::f]");

it should return all rows with formulas, but it doesn't return anything. The same xml on Oxygen Editor, when applied the same xpath expression, returns all of them.

I am copying WorksheetXml inner xml to assure the content is the same... do you know why C# is not working the expected way?

EDIT: Namespace issue

I've put this:

var manager = new XmlNamespaceManager(WorksheetXml.NameTable);
manager.AddNamespace(string.Empty, @"http://schemas.openxmlformats.org/spreadsheetml/2006/main");
manager.AddNamespace("r", @"http://schemas.openxmlformats.org/officeDocument/2006/relationships");

var nodeList = WorksheetXml.SelectNodes(@"//c[child::f]", manager);

and it didn't work, I think it is not a namespace problem.

btw, "//c[f]" would be simpler ;-p

Marc Gravell
– Marc Gravell

2009-07-08 20:06:10 +00:00
Commented Jul 8, 2009 at 20:06 — Marc Gravell
– Marc Gravell, Commented Jul 8, 2009 at 20:06

Community · Accepted Answer · 2017-05-23 12:13:35Z

3

Is it possible that Oxygen Editor is handling namespaces differently? My guess is that the c element is in a namespace, but you aren't specifying one.

See this very similar question for sample code - and if that's not the problem, please post more details.

EDIT: The code you've posted still doesn't use a namespace in the XPath. Try this:

var manager = new XmlNamespaceManager(WorksheetXml.NameTable);
manager.AddNamespace("n", 
    "http://schemas.openxmlformats.org/spreadsheetml/2006/main");
manager.AddNamespace("r",  
    "http://schemas.openxmlformats.org/officeDocument/2006/relationships");

var nodeList = WorksheetXml.SelectNodes("//n:c[child::n:f]", manager);

(I don't know which namespace the c and f elements are meant to be in - adjust appropriately.)

(Note that there's no need to use a verbatim string literal when you have no backslashes and the string is on one line.)

edited May 23, 2017 at 12:13

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answered Jul 8, 2009 at 20:02

Jon Skeet

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4 Comments

Victor Rodrigues Over a year ago

c element is from the default namespace. I've added a namespacemgr and it still doesn't return anything =/

Jon Skeet Over a year ago

And which is the default namespace here? I'm sure you don't mean the empty namespace. Do you mean main or relationships? See my edit.

Victor Rodrigues Over a year ago

I've resolved this issue without XPath, since it was not working and I had to deliver the code last week. Creating this 'n' -even if in xml this is the "empty" namespace, and c is just <c ...>...</c>- and handling c as n:c would help?

Jon Skeet Over a year ago

Yes, because it's not actually in the empty namespace, it's in the default namespace for that level of the document, as specified by an ancestor's xmlns="..." attribute.

Pavel Minaev · Accepted Answer · 2009-07-08 20:25:13Z

0

You did not specify OpenXML namespace for the nodes in your XPath expression. All stock .NET XPath APIs that I know of do not inherit any namespaces from document context - so if you do not explicitly specify it, and don't use any prefixes in XPath expression, it is treated as empty namespace.

Assuming that this is a call to XmlNode.SelectNode, you need the 2-argument overload where the second argument is XmlNamespaceManager.

answered Jul 8, 2009 at 20:25

Pavel Minaev

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2 Comments

Victor Rodrigues Over a year ago

I've changed the calling, passing manager as a parameter, and it still doesn't work =/

Pavel Minaev Over a year ago

It doesn't work because in XPath, an element without a prefix is always in the empty namespace (i.e. with no URI), regardless of what you do in XmlNamespaceManager. See w3.org/TR/xpath#node-tests: A QName in the node test is expanded into an expanded-name using the namespace declarations from the expression context. ... the default namespace declared with xmlns is not used: if the QName does not have a prefix, then the namespace URI is null (this is the same way attribute names are expanded). You have to use a prefix in your XPath for it to work.

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