Powershell - Replace in memory xml node while iterating

Question

I've got the following xml:

<messages>
  <message name="Advertisement" msgtype="7" msgcat="app">
    <field name="AdvId" required="Y" />
    <field name="AdvTransType" required="Y" />
    <field name="AdvRefID" required="N" />
    <component name="Instrument" required="Y" />
    <field name="AdvSide" required="Y" />
    <field name="Quantity" required="Y" />
  </message>
</messages>
<components>
  <component name="Instrument">
    <field name="Symbol" required="Y" />
    <field name="SymbolSfx" required="N" />
    <field name="SecurityID" required="N" />
    <field name="SecurityIDSource" required="N" />
    <group name="NoSecurityAltID" required="N">
      <field name="SecurityAltID" required="N" />
      <field name="SecurityAltIDSource" required="N" />
    </group>
    <field name="Product" required="N" />
    <field name="CFICode" required="N" />
  </component>
</components>

I want to iterate over each message and when I encounter a component tag, I want to replace the component xml with the fields/groups of the component.

I was attempting to use ReplaceChild, but it wasn't working as expected.

  [void]LoadComponents() {
    $this.xml.messages.message | ForEach-Object {
      $m = $_
      foreach ($node in $m.ChildNodes){
        if ($node.LocalName -eq "component") {
          Write-Host "Old Message: "
          Write-Host ($m.field | Format-Table | Out-String)
          $c = $this.GetComponent($node.name)
          Write-Host "Component: "
          Write-Host ($c.group | Format-Table | Out-String)
          $m.ReplaceChild($c, $node)
          Write-Host "New Message: "
          Write-Host ($m.field | Format-Table | Out-String)
        }
      }
    }
  }

  [System.Xml.XmlElement]GetComponent([string]$name) {
    return $this.xml.components.component | Where-Object { $_.name -eq $name }
  }

Edit:

I'm including the fact that I'm using powershell version 6.0.0.10 alpha on OSX, because apparently it's missing a lot of functionality.

woxxom · Accepted Answer · 2016-10-05 15:46:21Z

1

Use XPath to select the component nodes directly and clone the replacement node in ReplaceChild.

$xml.SelectNodes('/root/messages/message/component') | ForEach {
    $comp = $xml.SelectSingleNode('/root/components/component[@name="' + $_.name + '"]')
    $message = $_.ParentNode
    $message.ReplaceChild($comp.Clone(), $_)
}

The code is assuming the root node is root.

answered Oct 5, 2016 at 15:46

woxxom

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3 Comments

daino3 Over a year ago

Thanks @wOxxOm, but I'm getting [System.Xml.XmlDocument] does not contain a method named 'SelectNodes'

daino3 Over a year ago

powershell verion: 6.0.0 alpha

woxxom Over a year ago

I don't use buggy/incomplete alpha versions so I have no idea how it could miss such basic functionality. It's as absurd as a String without IndexOf.

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