Read xml file and how to modify logical operations using powershell

Question

$xml = [xml] @'
<?xml version="1.0" encoding="UTF-8"?>
<group>
    <product description="phone" id="1234/5678">
        <item name="apple" version="50" />
        <item name="banana" version="100" />
    </product>
    <product description="notebook" id="6666/7777">
        <item name="orange" version="150" />
    </product>
</group>
'@

$xml.group.product[0].item[0].name works (returns 'apple' ), because the 1st product element has 2 item child elements.

However, $xml.group.product[1].item[0].name does not work (returns $null ), because there is only one item element.

How can I reliably access the first item child element without having to know whether it happens to be the only one?

Answer 1

Your example xml isn't quite valid, so I'm going to use a slightly modified version:

$xml = [xml] @"
<?xml version="1.0" encoding="UTF-8"?>
<group>
  <product description="phone" id="1234/5678">
    <item name="apple" version="50" />
    <item name="banana" version="100" />
  </product>
  <product description="notebook" id="6666/7777">
    <item name="orange" version="150" />
  </product>
</group>
"@

In your scenario, there's a PowerShell feature called Member Enumeration which applies to your first product node and returns an array of all the child item nodes, but for the second product node it just returns the item node itself:

PS> $xml.group.product[0].item.GetType().FullName
System.Object[]

PS> $xml.group.product[1].item.GetType().FullName
System.Xml.XmlElement

As a result you can index into the array from the first product node, but not the XmlElement from the second, which gives the behaviour you've seen.

To fix this, what you could do is coerce the item nodes into an array so that you can index into it even if there's only one item :

PS> @($xml.group.product[0].item).GetType().FullName
System.Object[]

PS> @($xml.group.product[1].item).GetType().FullName
System.Object[]

PS> @($xml.group.product[1].item)[0].name
orange