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?

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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.

Answer 1

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.)

Answer 2

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.