How-to-close-all-positions

In the case of multiple entries, how can I ensure that when an exit signal occurs, all positions are closed simultaneously? When I use the following code, it only closes the initial entry position and does not close the additional positions.

CODE:
if (LastOpenPosition?.PositionType == PositionType.Short)
            {

               if ((index - 1 >= 0 && bars.Close[index] < BBlower[index - 1])
          
                  && bars.Close[index] < bars.Open[index]
                 
               {
                  Backtester.CancelationCode = 3;
                  _transaction = PlaceTrade(bars, TransactionType.Short, OrderType.Market, 0, 1, "ShortAdd");
                  count++;


               }


               else
               {
                  if (count > 1)
                  {
                     Backtester.CancelationCode = 4;
                     stops[index] = foundPosition1.TrailingStopPrice;
                     CloseAtTrailingStop(foundPosition1, TrailingStopType.ATR, Parameters[2].AsDouble, "Cover at Trailing Stop");
                  }


                  else
                  {
                     stops[index] = Math.Min(BBupper[index], stops[index - 1]);
                     Backtester.CancelationCode = 4;
                     _transaction = PlaceTrade(bars, TransactionType.Cover, OrderType.Stop, stops[index], 0, "Cover");