private void CancelBtn_Click(object sender, RoutedEventArgs e)
 {
     if (CheckInCheckOutDataGrid.SelectedItem == null)
     {
         MessageBox.Show("请选择一个订单!");
         return;
     }
     else if (searchbyRooms)
     {
         IRoom    rm   = CheckInCheckOutDataGrid.SelectedItem as IRoom;
         IBooking bk   = null;
         var      book = facade.GetActiveBookings(null);
         foreach (IBooking bktemp in book)
         {
             if (bktemp.RoomID == rm.ID)
             {
                 bk = bktemp;
                 break;
             }
         }
         try
         {
             if (bk != null)
             {
                 facade.CancelBooking(bk.ID);
                 MessageBox.Show("订单已取消");
                 facade.Log_Cancel(bk);
             }
         }
         catch (Exception ex)
         {
             MessageBox.Show("取消 Room 订单错误\n" + ex);
         }
     }
     else if (!searchbyRooms)
     {
         IBooking bk = CheckInCheckOutDataGrid.SelectedItem as IBooking;
         try
         {
             facade.CancelBooking(bk.ID);
             MessageBox.Show("订单已取消");
         }
         catch (Exception ex)
         {
             MessageBox.Show("取消 Booking 订单错误\n" + ex);
         }
     }
 }