The System.Xml.Linq namespace was added with .NET 3.5. This is known as LINQ to XML. Language Integrated Query (LINQ) is used to describe a query in the same language as the rest of a program. Therefore, interacting with a complex XML document does not require the use of XPath queries.

System.Xml.Linq is loaded by default in PowerShell Core. Windows PowerShell can make use of System.Xml.Linq once the required assembly has been added:

Add-Type -AssemblyName System.Xml.Linq 

This can also be phrased as follows:

using assembly System.Xml.Linq 

As a newer interface, System.Xml.Linq tends to be more consistent. The same syntax is used to create a document from scratch that is used to add elements and so on.