Powershell add an item to an xml array property

Question

i have a problem adding values to an xml array property. The xml looks like this:

$xml = [xml]@"
<letters>
    <letter><to>mail a</to></letter>
    <letter>
        <to>mail a</to>
        <to>mail b</to>
    </letter>
</letters>
"@

$letter = $xml.letters.letter[1]
$letter.to
#mail a
#mail b

now i want to add items ("mail c", "mail d") to the "to" array:

$letter.to
#mail a
#mail b
#mail c
#mail d

But i don't seem to be able to.

a) simply trying to set anything to the property results in a misleading error:

$letter.to += "a"
#"to" kann nicht festgelegt werden, da nur Zeichenfolgen als Werte zum Festlegen von XmlNode-Eigenschaften verwendet werden können.
#Bei Zeile:1 Zeichen:9
#+ $letter. <<<< to += "a"
#    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
#    + FullyQualifiedErrorId : PropertyAssignmentException

But that probably boils down to "to" not having a setter:

$letter | Get-Member
#Name       MemberType      Definition
#[bunch of stuff]
#to         Property        System.Object[] {get;}

b) Setting a value via SetAttribute partly works, but results in unusable (and very strange) behaviour:

$letter.SetAttribute("to", "mail c")
$letter.to
#mail c     <- why is it up front?
#mail a
#mail b

$letter.SetAttribute("to", "mail d")
$letter.to
#mail d     <- why is mail c gone?
#mail a
#mail b

Does anyone have an Idea what to try next?

har07 · Accepted Answer · 2016-02-23 11:53:31Z

2

Basically, you want to create a new XmlElement, set the InnerText value, and append it to the parent <letter> element :

$to = $xml.CreateElement("to")
$to.InnerText = "mail c"
$letter.AppendChild($to)
$letter.to

Output :

mail a
mail b
mail c

Similar example can be found in the MSDN documentation of XmlNode.AppendChild().

answered Feb 23, 2016 at 11:53

har07

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Harald F. · Accepted Answer · 2016-02-23 11:54:51Z

1

This will do the trick, you can create a fragment and add the innerxml for the to tag (since it's unstructured):

$letter = $xml.letters.letter[1]
$to= $xml.CreateDocumentFragment();
# Create the to node
$to.InnerXml = "<to>mail c</to>"
$letter.AppendChild($to);
# show the node
$letter

Altarnatively you could create the to tag on the document with the following:

$to = $xml.CreateElement("to")

Then set it's property (inner text) :

$to.InnerText = "mail c"

And append the item with

$letter.AppendChild($to)

answered Feb 23, 2016 at 11:54

Harald F.

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