Identifying a particular node in XML using PowerShell

Question

I am working with an XML document and I am not sure how to parse it to find a particular node.

In the example below I'd be searching for the ProductB and expecting to identify the Bee Hive

<PRODUCTS>
    <PRODUCT_LEVEL_1>
        <PRODUCT_ID>ProductA</PRODUCT_ID>
        <PRODUCT_NAME>Ant Hill</PRODUCT_NAME>
        <PRODUCT_ID>ProductB</PRODUCT_ID>
        <PRODUCT_NAME>Bee Hive</PRODUCT_NAME>
        <PRODUCT_ID>ProductC</PRODUCT_ID>
        <PRODUCT_NAME>Centipede Hotel</PRODUCT_NAME>
    </PRODUCT_LEVEL_1>
</PRODUCTS>

I'm not even sure how to refer to this format of XML which is making it difficult to search for.

Any assistance gratefully received.

Edit: At present I am loading the XML from a file using the following:

System.Xml.XmlDocument] $xd = new-object System.Xml.XmlDocument
$file = resolve-path($inputFile)
$xd.load($file)
$nodelist = $xd.selectnodes("/PRODUCTS/PRODUCT_LEVEL_1")
foreach ($documentNode in $nodelist) {
    #do some stuff
}

The actual XML file has loads of other junk in too but I stripped it out in the hopes of focusing on the bits I need. Perhaps I have stripped too much and the context has been lost?

Answer 1

You can use XPath for this task. XPath have axes, which allows you to refer preceding and following elements of document:

filter Prepare-StringForXPath {
    param(
        [Parameter(ValueFromPipeline)]
        [String]$String
    )
    if($String -notlike '*''*') {
        "'$String'"
    } elseif($String -notlike '*"*') {
        """$String"""
    } else {
        “concat($(($String -split '(?<=''[^"]*)(?=")|(?<="[^'']*)(?='')' | Prepare-StringForXPath) -join ', '))”
    }
}

$xd = [Xml]@'
<PRODUCTS>
    <PRODUCT_LEVEL_1>
        <PRODUCT_ID>ProductA</PRODUCT_ID>
        <PRODUCT_NAME>Ant Hill</PRODUCT_NAME>
        <PRODUCT_ID>ProductB</PRODUCT_ID>
        <PRODUCT_NAME>Bee Hive</PRODUCT_NAME>
        <PRODUCT_ID>ProductC</PRODUCT_ID>
        <PRODUCT_NAME>Centipede Hotel</PRODUCT_NAME>
    </PRODUCT_LEVEL_1>
</PRODUCTS>
'@

$ProdName = Read-Host 'Input product name'
$ProdID = $xd.SelectSingleNode("//PRODUCT_NAME[.=$(Prepare-StringForXPath $ProdName)]/preceding-sibling::PRODUCT_ID[1]").InnerText
"Product ID for '$ProdName' is '$ProdID'."

$ProdID = Read-Host 'Input product ID'
$ProdName = $xd.SelectSingleNode("//PRODUCT_ID[.=$(Prepare-StringForXPath $ProdID)]/following-sibling::PRODUCT_NAME[1]").InnerText
"Product name for '$ProdID' is '$ProdName'."