Working with XML Files

Accessing an XML File

<!-- file.xml -->
<people>
    <person id="101">
        <name>Jon Lajoie</name>
        <age>22</age>
    </person>
    <person id="102">
        <name>Lord Gaben</name>
        <age>65</age>
    </person>
    <person id="103">
        <name>Gordon Freeman</name>
        <age>29</age>
    </person>
</people>

Loading an XML File

To load an XML file, you can use any of these:

# First Method
$xdoc = New-Object System.Xml.XmlDocument
$file = Resolve-Path(".\file.xml")
$xdoc.load($file)

# Second Method
[xml] $xdoc = Get-Content ".\file.xml"

# Third Method
$xdoc = [xml] (Get-Content ".\file.xml")

Accessing XML as Objects

PS C:\> $xml = [xml](Get-Content file.xml)
PS C:\> $xml

PS C:\> $xml.people

person
--------
{Jon Lajoie, Lord Gaben, Gordon Freeman}

PS C:\> $xml.people.person

id                                      name                                    age
--                                      ----                                    ---
101                                     Jon Lajoie                              22
102                                     Lord Gaben                              65
103                                     Gordon Freeman                          29

PS C:\> $xml.people.person[0].name
Jon Lajoie

PS C:\> $xml.people.person[1].age
65

PS C:\> $xml.people.person[2].id
103

Accessing XML with XPath

PS C:\> $xml = [xml](Get-Content file.xml)
PS C:\> $xml

PS C:\> $xml.SelectNodes("//people")

person
--------
{Jon Lajoie, Lord Gaben, Gordon Freeman}

PS C:\> $xml.SelectNodes("//people//person")

id                                      name                                    age
--                                      ----                                    ---
101                                     Jon Lajoie                              22
102                                     Lord Gaben                              65
103                                     Gordon Freeman                          29

PS C:\> $xml.SelectSingleNode("people//person[1]//name")
Jon Lajoie

PS C:\> $xml.SelectSingleNode("people//person[2]//age")
65

PS C:\> $xml.SelectSingleNode("people//person[3]//@id")
103

Accessing XML containing namespaces with XPath

PS C:\> [xml]$xml = @"
<ns:people xmlns:ns="http://schemas.xmlsoap.org/soap/envelope/">
    <ns:person id="101">
        <ns:name>Jon Lajoie</ns:name>
    </ns:person>
    <ns:person id="102">
        <ns:name>Lord Gaben</ns:name>
    </ns:person>
    <ns:person id="103">
        <ns:name>Gordon Freeman</ns:name>
    </ns:person>
</ns:people>
"@

PS C:\> $ns = new-object Xml.XmlNamespaceManager $xml.NameTable
PS C:\> $ns.AddNamespace("ns", $xml.DocumentElement.NamespaceURI)
PS C:\> $xml.SelectNodes("//ns:people/ns:person", $ns)

id                                      name
--                                      ----
101                                     Jon Lajoie
102                                     Lord Gaben
103                                     Gordon Freeman

Creating an XML Document using XmlWriter()

# Set The Formatting
$xmlsettings = New-Object System.Xml.XmlWriterSettings
$xmlsettings.Indent = $true
$xmlsettings.IndentChars = "    "

# Set the File Name Create The Document
$XmlWriter = [System.XML.XmlWriter]::Create("C:\YourXML.xml", $xmlsettings)

# Write the XML Decleration and set the XSL
$xmlWriter.WriteStartDocument()
$xmlWriter.WriteProcessingInstruction("xml-stylesheet", "type='text/xsl' href='style.xsl'")

# Start the Root Element
$xmlWriter.WriteStartElement("Root")

    $xmlWriter.WriteStartElement("Object") # <-- Start <Object>

        $xmlWriter.WriteElementString("Property1","Value 1")
        $xmlWriter.WriteElementString("Property2","Value 2")

        $xmlWriter.WriteStartElement("SubObject") # <-- Start <SubObject>
            $xmlWriter.WriteElementString("Property3","Value 3")
        $xmlWriter.WriteEndElement() # <-- End <SubObject>

    $xmlWriter.WriteEndElement() # <-- End <Object>

$xmlWriter.WriteEndElement() # <-- End <Root>

# End, Finalize and close the XML Document
$xmlWriter.WriteEndDocument()
$xmlWriter.Flush()
$xmlWriter.Close()

Output XML File

<?xml version="1.0" encoding="utf-8"?>
<?xml-stylesheet type='text/xsl' href='style.xsl'?>
<Root>
    <Object>
        <Property1>Value 1</Property1>
        <Property2>Value 2</Property2>
        <SubObject>
            <Property3>Value 3</Property3>
        </SubObject>
    </Object>
</Root>

Adding snippits of XML to current XMLDocument

Sample Data

XML Document

First, let’s define a sample XML document named “books.xml” in our current directory:

New Data

What we want to do is add a few new books to this document, let’s say Patriot Games by Tom Clancy (yes, I’m a fan of Clancy’s works ^__^) and a Sci-Fi favourite: The Hitchhiker’s Guide to the Galaxy by Douglas Adams mainly because Zaphod Beeblebrox is just fun to read.

Somehow we’ve acquired the data for the new books and saved them as a list of PSCustomObjects:

Templates

Now we need to define a few skeleton XML structures for our new data to go into. Basically, you want to create a skeleton/template for each list of data. In our example, that means we need a template for the book, characters, and publishers. We can also use this to define a few default values, such as the value for the film tag.

We’re done with set-up.

Adding the new data

Now that we’re all set-up with our sample data, let’s add the custom objects to the XML Document Object.

We can now write our XML to disk, or screen, or web, or wherever!

Profit

While this may not be the procedure for everyone I found it to help avoid a whole bunch of [void]$xml.SelectSingleNode("/complicated/xpath/goes[here]").AppendChild($xml.CreateElement("newElementName") followed by $xml.SelectSingleNode("/complicated/xpath/goes/here/newElementName") = $textValue

I think the method detailed in the example is cleaner and easier to parse for normal humans.

Improvements

It may be possible to change the template to include elements with children instead of breaking out each section as a separate template. You just have to take care to clone the previous element when you loop through the list.