XML on windows phone 7

I am a newbie in windows phone 7. I want to do some demo within XML but I can't find the XMLDocument class (like what I do on Windows Form). I开发者_开发知识库 can't find the namespace Linq, XPath... in System.Xml also (see below picture).

There is a separate assembly for it that you will need to reference (System.Xml.Linq). Once you have that you will be able to use the Linq 2 XML stuff (XDocument, etc). XmlDocument isn't available in Silverlight (and therefore is not available in WP7).

Jay