/// <summary>
        /// This turns the Birds-Eye-Viewer on and off
        /// </summary>
        private void OnShowBev()
        {
            IsBevShowing = !IsBevShowing;
            BirdsEyeViewModel bev = BirdsEyeViewModel;

            if (IsBevShowing)
            {
                bev.Show();
                bev.SetActiveViewModel(this);
            }
            else
            {
                bev.CloseView.Execute(null);
            }
        }