I have an XML document that contains two namespaces (the \'default\' namespace and xlink):
Figured it out. Had to use $null for the prefix of the default namespace ($null is equivalent to String.Empty in C#).
Working code:
[System.Xml.XmlNamespaceManager] $nsmgr = $xml.NameTable;
$nsmgr.AddNamespace($null,'http://embassy/schemas/dudezilla/');
$nsmgr.AddNamespace('xlink','http://www.w3.org/1999/xlink');
[System.Xml.XmlNodeList] $nodelist;
[System.Xml.XmlElement] $root = $xml.DocumentElement;
$nodelist = $root.SelectNodes("//image/@xlink:href", $nsmgr);
Foreach ($xmlnode in $nodelist)
{
$xmlnode.Value;
}