XPath query working in XPath tester, but not in VB.NET

Question

Why does this XPath return a result in XPath Tester, but not in my code? I think that I'm overlooking something simple.

Sub Main()
    Dim doc As New XmlDocument()
    doc.Load(AppDomain.CurrentDomain.SetupInformation.ConfigurationFile)

    Dim xmlNode As XmlElement = TryCast(doc.SelectSingleNode("/configuration/Status"), XmlElement)
    Dim xpath = "/Status/ElementOne[@ID='1234']"

    Console.WriteLine(xmlNode.OuterXml)

    Console.WriteLine()

    Console.WriteLine(xpath)

    Dim eFileEvent = xmlNode.SelectSingleNode(xpath)

    Console.WriteLine()
    Console.WriteLine("Results")

    If (eFileEvent Is Nothing) Then
        Return
    End If

    Console.WriteLine(eFileEvent.OuterXml)
End Sub

Config:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
...
  <configSections>
    <section name="Status" type="System.Configuration.IgnoreSectionHandler,     System, Version=1.0.5000.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"
         allowLocation="false" />
  </configSections>
  <Status xmlns="">
    <ElementOne ID="1234"></ElementOne>
  </Status>
</configuration>

har07 · Accepted Answer · 2014-07-19 01:21:14Z

2

It isn't clear how you did the test in XPath tester (or what exactly the XPath expression you tested), but I think your code is fair to fail because it is trying to get node having path configuration -> Status -> Status -> ElementOne which clearly doesn't exist :

Dim xmlNode As XmlElement = TryCast(doc.SelectSingleNode("/configuration/Status"), XmlElement)
Dim xpath = "/Status/ElementOne[@ID='1234']"

You can either fix the xpath variable value this way :

Dim xpath = "ElementOne[@ID='1234']"

or this way (single period (.) at the beginning is mandatory) :

Dim xpath = "./ElementOne[@ID='1234']"

or if possible, just get the right node in one line :

Dim xmlNode As XmlElement = doc.SelectSingleNode("/configuration/Status/ElementOne[@ID='1234']")

answered Jul 19, 2014 at 1:21

har07

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1 Comment

Hoppe Over a year ago

I'm mocking some data through the web.config temporarily. I didn't realize that when I ran the second xpath query, starting the query with '/' took me back to the root of the xml. As you stated, I had to drop the forward slash, or use a period. Many thanks

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