add a root element using xmldocument in C#.net

I need to create an XML file using an xmldocument object in C#.

How can I add a root element like:

 book:aaaa xsi:schemalocat开发者_如何学JAVAionchemaLocation="http://www.com"

---

XmlDocument doc = new XmlDocument();
XmlElement elem = doc.CreateElement("book", "aaaa", "http://www.com");
doc.AppendChild(elem);