Updating array element in xml document

Question

This code:

$test = @"
<Test>
  <Child>Hello</Child>
  <Child>World</Child>
</Test>
"@

$xml = [xml]$test
$xml.Test.Child[1]

yields:

World

Then this code:

$xml.Test.Child[1] = "StackOVerflow"
$xml.InnerXml

yields:

<Test><Child>Hello</Child><Child>World</Child></Test>

Why the second Child node is not getting updated from World to StackOverflow?

Okay, let's try something different:

$ipaddress=([System.Net.DNS]::GetHostAddresses($hostname)|Where-Object {$_.AddressFamily -eq "InterNetwork"}   |  select-object IPAddressToString)[0].IPAddressToString

Now I wonder what the type of $ipaddress is:

$ipaddress.GetType()

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     String                                   System.Object

Apparently it's string.

$xml.Test.ChildNodes[1].'#text' = $ipaddress
Cannot set "#text" because only strings can be used as values to set XmlNode properties.
At line:1 char:1
+ $xml.Test.ChildNodes[1].'#text' = $ipaddress
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [], SetValueException
    + FullyQualifiedErrorId : XmlNodeSetShouldBeAString

But $ipaddress is string!

This finally works:

$xml.Test.ChildNodes[1].'#text' = [string]$ipaddress

What's going on?

David Brabant · Accepted Answer · 2017-04-05 10:47:58Z

1

Seems to be related to a bug that might have been fixed in PowerShell 6. I don't have a Linux machine at hand to check.

You'll find a description of that bug here.

Meanwhile, there is a workaround, as you have found it:

$test = @"
<Test>
  <Child>Hello</Child>
  <Child>World</Child>
</Test>
"@

$xml = [xml]$test
$xml.Test
$xml.Test.GetType()                 # = XmlElement

$xml.Test.Child[1]                      # = World
$xml.Test.Child[1].GetType()            # = String

$xml.Test.Child[1] = "Tralala"
$xml.Test.Child[1]                      # = World


$xml.Test.ChildNodes.Item(1).GetType()  # = XmlElement
$xml.Test.ChildNodes.Item(1)."#text" = "StackOverflow"
$xml.Test.Child[1]                      # = StackOverflow

edited Apr 5, 2017 at 10:47

answered Apr 5, 2017 at 10:37

David Brabant

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2 Comments

David Brabant Over a year ago

Same behavior on PowerShell 6.0.0-alpha.13

Andrew Savinykh Over a year ago

Thank you for this, but as you might have noticed, I've posted the same work around in the original question itself.

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