Fetching an attribute value from XPath of an XML using powershell

Question

I am having an issue with getting and setting attribute value from XPath of an XML Config File using powershell. Attributes are like

"<add key="TransactDeadLetterQueueThreshold" value="0" />".

Sample XML File :

    <?xml version="1.0" encoding="utf-8"?>
    <configuration>
      <appSettings>
        <add key="ReportFile" value="C:\Program Files\Fusion\Viewer Suite Monitoring\ViewersMonitoring\monitor.txt" />
    <add key="QueueThreshold" value="1000" />
    <add key="TransactDeadLetterQueueThreshold" value="0" />
    <add key="TimeCardsThreshold" value="6000" />
    <add key="PercentDiskSpaceThreshold" value="10" />
    <add key="QueueCreatedFormat" value="The {0} queue is created." />
    <add key="QueueOverThresholdFormat" value="The {0} queue size is larger than {1} messages." />
    <add key="QueueTransactDeadLetterOverThresholdFormat" value="The transactional dead queue size is larger than {0} messages." />
    <add key="DriveThresholdFormat" value="The {0} drive space is less than {1}." />
    <add key="QueueRemovedFormat" value="The {0} queue is removed." />
    <add key="TimeCardsOverThresholdFormat" value="The time card records count is greater than or equal to {0} ." />
    <add key="FailedConnectDbFormat" value="Failed: unable to access the database, reason: {0}" />
    <add key="LogName" value="Viewer Suite Monitor" />
    <add key="ViewersPrivateQueues" value="private$\adt,private$\infusionviewer,private$\timecards" />
    <add key="DrivetobeMonitored" value="D:" />
  </appSettings>

I tried to grab the attribute the following way :

$xdoc = Get-content "C:\Program Files\Fusion\Viewer Suite Monitoring\CareFusion.Infusion.ViewerSuite.Monitoring.exe.config"


$value = ($xdoc.configuration.appSettings.SelectSingleNode(add[@key = "PercentDiskSpaceThreshold"])) + $value.GetAttribute('key')

and also tried this way :

$xdoc = Get-Content "C:\Program Files\Fusion\Viewer Suite Monitoring\Fusion.ViewerSuite.Monitoring.exe.config"
$value = $xdoc.selectSingleNode("/configuration/appSettings/add[@key = ""TransactDeadLetterQueueThreshold""] ")'+"
$value.GetAttribute('key')"

I am getting errors. I do not know what is wrong with this. Please help.

possible duplicate of PowerShell to get attribute values from XML with multiple attributes — Alexander Obersht
– Alexander Obersht, Commented Sep 19, 2015 at 17:34
What are you trying to accomplish with + $value.GetAttribute('key') at the end of the assignment to $value? — Mathias R. Jessen
– Mathias R. Jessen, Commented Sep 19, 2015 at 17:56

Keith Hill · Accepted Answer · 2015-09-20 03:16:27Z

1

Here's an alternative which relies more on PowerShell and less on the .NET XML API:

# Get the attribute value
$xdoc = [xml](Get-Content <path-to-xml-file>)
$key = $xml.configuration.appsettings.add | Where {$_.Key -eq 'TransactDeadLetterQueueThreshold'}
$key.Value

# Set the attribute
$key.Value = '1'

You still need to use $xdoc.Save(<path>) to save the changes to file.

edited Sep 20, 2015 at 3:16

answered Sep 19, 2015 at 20:06

Keith Hill

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3 Comments

9009 Over a year ago

My intent is to initially try and get the attribute value and update the attribute value with the required value.I had tried the solution but the an error is throwing with this exception :+ $key = $xml.configuration.appSettings.add | where <<<< Key -eq TransactDeadLetterQueueThreshold + CategoryInfo : InvalidArgument: (:) [Where-Object], ParameterBindingException + FullyQualifiedErrorId : CannotConvertArgumentNoMessage,Microsoft.PowerShell.Commands.WhereObjectCommand

Keith Hill Over a year ago

When you post questions about PowerShell be sure to add which version of PowerShell you are using as a tag. Are you on V2? If so, try the updated answer.

9009 Over a year ago

magical - Thank you very much Keith. This had worked brilliantly. This code worked on both v1.0 and v2.0.

Mathias R. Jessen · Accepted Answer · 2015-09-19 18:02:06Z

0

You're on the right track.

Make sure PowerShell treats the XML as an actual XmlDocument object with the [xml] type accelerator:

$XmlPath = '.\path\to\app.config'
$XDoc = [xml](Get-Content $XmlPath)

Select the node whose value you want to change:

$TransactDeadLetterNode = $XDoc.SelectSingleNode('//add[@key = "TransactDeadLetterQueueThreshold"]')

Set the attribute:

$TransactDeadLetterNode.SetAttribute("value",1)

(repeat for any other node you want to change)
And finally save the document:

$XDoc.Save($XmlPath)

answered Sep 19, 2015 at 18:02

Mathias R. Jessen

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