I'd like to handle the Closing event (when a user clicks the upper right 'X' button) of my window in order to eventually display a confirm message or/and cancel the closing. I know how to do this in the code-behind: subscribe to the Closing event of the window then use the CancelEventArgs.Cancel property. But I'm using MVVM so I'm not sure it's the good approach. I think the good approach would be
![Handling the window closing event with WPF / MVVM Light Toolkit](https://cdn-ak-scissors.b.st-hatena.com/image/square/98d6f053a97a87156775f60757c60865d0f2c47d/height=288;version=1;width=512/https%3A%2F%2Fcdn.sstatic.net%2FSites%2Fstackoverflow%2FImg%2Fapple-touch-icon%402.png%3Fv%3D73d79a89bded)