Basically when user resizes my application\'s window I want application to be same size when application is re-opened again.
At first I though of handling SizeChange
Actually you don't need to use code-behind to do that (except for saving the settings). You can use a custom markup extension to bind the window size and position to the settings like this :
You can find the code for this markup extension here : http://www.thomaslevesque.com/2008/11/18/wpf-binding-to-application-settings-using-a-markup-extension/