ExecutionPrice-is-zero

That’s because the execution price is not known until the following bar, or the following iteration of the Execute method.

See the example for Position > EntryPrice. Whoops, no example in the QuickRef, but we'll fix that.. here it is:

CODE:
using WealthLab.Backtest;
using System;
using WealthLab.Core;
using WealthLab.Indicators;
using System.Drawing;
using System.Collections.Generic;

namespace WealthScript2
{
   public class EntryBarExample : UserStrategyBase
   {
      IndicatorBase _ma;

      public override void Initialize(BarHistory bars)
      {
         StartIndex = 20;
         _ma = SMA.Series(bars.Close, 20);
         PlotIndicatorLine(_ma);
         PlotStopsAndLimits(4);
      }

      //execute the strategy rules here, this is executed once for each bar in the backtest history
      public override void Execute(BarHistory bars, int idx)
      {
         if (!HasOpenPosition(bars, PositionType.Long))
         {
            if (bars.Close.CrossesOver(_ma, idx))
               PlaceTrade(bars, TransactionType.Buy, OrderType.Market);
         }
         else
         {
            Position p = LastPosition;
            if (idx - p.EntryBar + 1 > 5)               
               PlaceTrade(bars, TransactionType.Sell, OrderType.Market, 0, "Time-based");
            else
            {
               double limit = p.EntryPrice * 1.05;     // 5% profit target
               PlaceTrade(bars, TransactionType.Sell, OrderType.Limit, limit, "5%");
            }
         }
      }
   }
}