Programmer - Silverlight stop page closing before being saved

Programmer Question

Here's a question for all you Silverlight guys.

In the old days for WinForms, if your user was creating/editing some information in a DialogBox, it was easy to detect the Window closing and if the data was dirty, ask if they wanted to save.

My question is, how do you approach this scenario in Silverlight where everything seems to be done in UserControls, which have no obvious way of knowing when the page is closing.

There must be some standard way of acheiving this?