OnBackKeyPress 后退键的禁止

protected override void OnBackKeyPress(System.ComponentModel.CancelEventArgs e)
        {
            base.OnBackKeyPress(e);

            if (!MessageBox.Show("Are you sure to give up current Trip?", "Trip Edit", MessageBoxButton.OKCancel).Equals(MessageBoxResult.OK))
            {
                e.Cancel = true;
            }
        }