Below is a sample code snippet demonstrating how to cancel Navigation Programatically in the OnBackKeyPress Event in WP8?
How to Cancel Navigation Programatically in the OnBackKeyPress Event in WP8?
protected override void OnBackKeyPress(System.ComponentModel.CancelEventArgs e)
{
if (MessageBox.Show("Stay in Abundantcode.com", "Ask", MessageBoxButton.OKCancel) == MessageBoxResult.Yes)
e.Cancel = false;
base.OnBackKeyPress(e);
}