XPath query works with online tools but not in .NET

Question

I am able to get the below xpath to work against the below xml with online xpath tools but I am getting an "Expression must evaluate to a node-set." exception in .NET 4.5

xpath:

//*[starts-with(name(.), "childnode")[identification/text()='xyz']]

xml:

<rootnode>
    <childnode1234>
        <identification>xyz</identification>
    </childnode1234>
    <childnode3456>
        <identification>abc</identification>
    </childnode3456>
 </rootnode>

The expected result is

<childnode1234>
            <identification>xyz</identification>
        </childnode1234>

Did you copy your XPath correctly? What is the "; at the end supposed to mean? — svick
– svick, Commented Jan 26, 2013 at 2:26
Please show real C# string - right now it contains non-escaped double-quotes... — Alexei Levenkov
– Alexei Levenkov, Commented Jan 26, 2013 at 2:47
The testers I've tried are: xpathtester.com/test & freeformatter.com/xpath-tester.html. I am escaping the " with \". The expected result is: <childnode1234> <identification>xyz</identification> </childnode1234> — kevinc
– kevinc, Commented Jan 26, 2013 at 2:58

Dimitre Novatchev · Accepted Answer · 2013-01-26 03:58:58Z

4

Just change:

//*[starts-with(name(.), "childnode")[identification/text()='xyz']]

to:

//*[starts-with(name(.), "childnode")][identification/text()='xyz']

I recommend to avoid untested and obviously buggy "no name" "online xpath tools".

answered Jan 26, 2013 at 3:58

Dimitre Novatchev

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1 Comment

Dimitre Novatchev Over a year ago

@RossPatterson, Yes, there are a number of these that attract newbies -- only to find that they aren't compliant XPath implementations.

Anton Tykhyy · Accepted Answer · 2013-01-26 03:09:10Z

3

The online implementations are too relaxed. Microsoft XPath is right: starts-with() evaluates to a boolean, not to a node-set. Try

//*[starts-with(name(.), 'childnode') and identification/text()='xyz']

answered Jan 26, 2013 at 3:09

Anton Tykhyy

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1 Comment

Ross Patterson Over a year ago

+1 because I think //*[x and y] is stylistically preferable to //*[x][y], even though they're equivalent.

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