BuildXML.ps1

"This:"
"<queryxml version='1.0'><entity>Ticket</entity><query><field>TicketNumber<expression op='Equals'>135481</expression></field></query></queryxml>"
"should equal this:"

$doc = new-object System.Xml.XmlDocument
$root = $doc.CreateElement("queryxml")
$root.SetAttribute("version","1.0")
$entity = $doc.CreateElement("entity")
$entity.InnerText = "Ticket"
$query = $doc.CreateElement("query")
$field = $doc.CreateElement("field")
$field.InnerText = "TicketNumber"
$expression = $doc.CreateElement("expression")
$expression.SetAttribute("op","Equals")
$expression.InnerText = "135481"

[void]$field.AppendChild($expression)
[void]$query.AppendChild($field)
[void]$root.AppendChild($entity)
[void]$root.AppendChild($query)
[void]$doc.AppendChild($root)
$doc.OuterXml

This is a much easier way to logically build an xml file in Powershell. Build from the bottom up.