How-to-access-OpenPositions-Count-bars-ago-in-the-Execute-loop

You’d maintain your own List int to store the open position count and add the value each Execute loop.

Why declaring TimeSeries OpenPosSeries; OpenPosSeries= new TimeSeries(bars.DateTimes, 0);

and assigning OpenPosSeries[idx] = OpenPositions.Count; in the Execute loop does not work?

Open positions count is not known in Execute() yet.
Keep track of the filled transactions in Execute and update a static int var.
In Cleanup() assign it to your static TimeSeries.
See the BLOG article about the inner workings for details.

https://www.wealth-lab.com/blog/anatomy-of-a-wl7-strategy

@wl64bit - It works, but OpenPositions.Count only gives the count for the bars being processed (one symbol).
For the count for all open positions, use OpenPositionsAllSymbols.Count();

CODE:
      TimeSeries OpenPosSeries; 
      public override void Initialize(BarHistory bars)
      {
         OpenPosSeries = new TimeSeries(bars.DateTimes, 0);
         PlotTimeSeries(OpenPosSeries, "Open Positions", "OpenPos", WLColor.Green, PlotStyle.Histogram);
      }
      public override void Execute(BarHistory   bars, int idx)
      {
         OpenPosSeries[idx] = OpenPositionsAllSymbols.Count();
         :
         :