private void btnManageAreas_Click(object sender, System.Windows.RoutedEventArgs e)
        {
            if (_manageAreasWindow == null)
            {
                _manageAreasWindow = new ManageAreasWindow();
                _manageAreasWindow.Closed += Window_Closed;
            }

            _manageAreasWindow.Show();
            _manageAreasWindow.WindowState = WindowState.Normal;
        }
 void Window_Closed(object sender, EventArgs e)
 {
     if (sender is ManageAreasWindow)
     {
         _manageAreasWindow = null;
     }
     else if (sender is ManagePatientsWindow)
     {
         _managePatientNotesWindow = null;
     }
 }