I can't extract the node text with a Xpath - xpath

Question

I have a XML file (test.xml) like this one:
<?xml version="1.0" encoding="ISO-8859-1"?>
<s2xResponse>
<s2xData>
<Name>This is the name</Name>
<InfocomData>
<DateOfUpdate day="07" month="02" year="2018">20180207</DateOfUpdate>
<CompanyName>MY COMPANY</CompanyName>
<TaxCode FlagCheck="0">XXXYYYWWWZZZ</TaxCode>
</InfocomData>
<AssessmentSummary>
<Rating Code="2">Rating Description for Code 2</Rating>
</AssessmentSummary>
<AssessmentData>
<SectorialDistribution>
<CompaniesNumber>11650</CompaniesNumber>
<ScoreDistribution />
<CervedScoreDistribution>
<DistributionData>
<Rating Code="1">SICUREZZA</Rating>
<Percentage>1.91</Percentage>
</DistributionData>
<DistributionData>
<Rating Code="2">SOLVIBILITA' ELEVATA</Rating>
<Percentage>35.56</Percentage>
</DistributionData>
</CervedScoreDistribution>
</SectorialDistribution>
</AssessmentData>
</s2xData>
</s2xResponse>
I'm trying to get the "Name" node text ("This is the name") with a U-SQL script using the XmlExtractor. The following is the code I'm using:
USE TestXML; // It contains the registered assembly
REFERENCE ASSEMBLY [Microsoft.Analytics.Samples.Formats];
#xml = EXTRACT xml_text string
FROM "textxpath/test.xml"
USING Extractors.Text(rowDelimiter: "^", quoting: false);
#xml_cleaned =
SELECT
xml_text.Replace("\r\n", "").Replace("\t", " ") AS xml_text
FROM #xml;
#values =
SELECT Microsoft.Analytics.Samples.Formats.Xml.XPath.Evaluate(xml_text, "s2xResponse/s2xData/Name")[1] AS value
FROM #xml_cleaned;
OUTPUT #values TO #"outputs/test_xpath.txt" USING Outputters.Text(quoting: false);
But I'm getting this runtime error:
Execution failed with error '1_SV1_Extract Error :
'{"diagnosticCode":195887116,"severity":"Error","component":"RUNTIME","source":"User","errorId":"E_RUNTIME_USER_EXPRESSIONEVALUATION","message":"Error
while evaluating expression
Microsoft.Analytics.Samples.Formats.Xml.XPath.Evaluate(xml_text.Replace(\"\r\n\",
\"\").Replace(\"\t\", \" \"),
\"s2xResponse/s2xData/Name\")[1]","description":"Inner exception from
user expression: Index was out of range. Must be non-negative and less
than the size of the collection.
I get the same error even if I use a zero index for the Evaluate result ([0]).
What's wrong with my query?

Answer 1

The problem here is that you are applying the subscript [1] to the result of XPath.Evaluate, which I believe will be returning the Name nodes. However, you are applying the [1] subscript in code, not in XPath, so the subscript is likely to be zero based, and not 1-based as it is in XPath, hence the Index out of range error.
Here's one solution - simply apply the subscript operator in Xpath (where it is still 1-based), and select the text() there
.Evaluate("s2xResponse/s2xData/Name[1]/text()")

Answer 2

Is there a particular reason you want to use the Evaluate method? I got his to work using the XmlDomExtractor, which would allow you to extract multiple values from the xml, eg
REFERENCE ASSEMBLY [Microsoft.Analytics.Samples.Formats];
DECLARE #inputFile string = "/input/input100.xml";
#input =
EXTRACT Name string
FROM #inputFile
USING new Microsoft.Analytics.Samples.Formats.Xml.XmlDomExtractor(rowPath : "/s2xResponse",
columnPaths : new SQL.MAP<string, string>{
{ "s2xData/Name", "Name" },
}
);
#output =
SELECT *
FROM #input;