XML data binding in metro style app using c#

Hi,

I m working on C# and XAML on metro applications. I want to access data from a XML file and if any data is added to the UI, it is saved in the XML file. I have never worked on XML before. 

Till now I have created ObservableCollection list and it is binded to a ListView. For now i have hard-coded the values for the list. Now what i want to do is:

say i have stored some 10 default values in the list in the XML file. The XML file should return this list and ListView should show these 10 values in the user interface, when user changes anythg, it should be reflected in the XML file also and if uses adds some new values.. it should be added to XML file...so that if it is loaded again...in the user interface it should have those default values as well as values added by the user.

I tried serahcing on ths but nt able to figure out how i have to implement ths. Any links and samples will be helpful.