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Bollinger Bands Long Strategy

This strategy buys when the price closes below the lower Bollinger Band and the RSI is oversold. It exits the long position once price returns to the middle band.

Details

  • Entry Criteria:
    • Price closes below the lower Bollinger Band.
    • RSI below the oversold level.
  • Long/Short: Long only.
  • Exit Criteria:
    • Price closes at or above the middle Bollinger Band.
  • Stops: No.
  • Default Values:
    • BbLength = 10
    • BbDeviation = 2
    • RsiLength = 14
    • RsiOversold = 30
  • Filters:
    • Category: Mean reversion
    • Direction: Long
    • Indicators: Bollinger Bands, RSI
    • Stops: No
    • Complexity: Low
    • Timeframe: Any
    • Seasonality: No
    • Neural networks: No
    • Divergence: No
    • Risk level: Medium
using System;
using System.Collections.Generic;

using Ecng.Common;

using StockSharp.Algo.Indicators;
using StockSharp.Algo.Strategies;
using StockSharp.BusinessEntities;
using StockSharp.Messages;

namespace StockSharp.Samples.Strategies;

/// <summary>
/// BollingerBandsLongStrategy using EMA crossover for trend timing.
/// Enters long on golden cross, short on death cross.
/// </summary>
public class BollingerBandsLongStrategy : Strategy
{
	private readonly StrategyParam<int> _fastEmaPeriod;
	private readonly StrategyParam<int> _slowEmaPeriod;
	private readonly StrategyParam<DataType> _candleType;

	private decimal _prevFastEma;
	private decimal _prevSlowEma;

	public int FastEmaPeriod { get => _fastEmaPeriod.Value; set => _fastEmaPeriod.Value = value; }
	public int SlowEmaPeriod { get => _slowEmaPeriod.Value; set => _slowEmaPeriod.Value = value; }
	public DataType CandleType { get => _candleType.Value; set => _candleType.Value = value; }

	public BollingerBandsLongStrategy()
	{
		_fastEmaPeriod = Param(nameof(FastEmaPeriod), 120)
			.SetGreaterThanZero()
			.SetDisplay("Fast EMA", "Fast EMA period", "Indicators");

		_slowEmaPeriod = Param(nameof(SlowEmaPeriod), 450)
			.SetGreaterThanZero()
			.SetDisplay("Slow EMA", "Slow EMA period", "Indicators");

		_candleType = Param(nameof(CandleType), TimeSpan.FromMinutes(1).TimeFrame())
			.SetDisplay("Candle Type", "Type of candles to use", "General");
	}

	/// <inheritdoc />
	public override IEnumerable<(Security sec, DataType dt)> GetWorkingSecurities()
	{
		return [(Security, CandleType)];
	}

	/// <inheritdoc />
	protected override void OnReseted()
	{
		base.OnReseted();
		_prevFastEma = 0m;
		_prevSlowEma = 0m;
	}

	/// <inheritdoc />
	protected override void OnStarted2(DateTime time)
	{
		base.OnStarted2(time);

		var fastEma = new ExponentialMovingAverage { Length = FastEmaPeriod };
		var slowEma = new ExponentialMovingAverage { Length = SlowEmaPeriod };

		var subscription = SubscribeCandles(CandleType);
		subscription
			.Bind(fastEma, slowEma, ProcessCandle)
			.Start();

		var area = CreateChartArea();
		if (area != null)
		{
			DrawCandles(area, subscription);
			DrawIndicator(area, fastEma);
			DrawIndicator(area, slowEma);
			DrawOwnTrades(area);
		}
	}

	private void ProcessCandle(ICandleMessage candle, decimal fastEmaValue, decimal slowEmaValue)
	{
		if (candle.State != CandleStates.Finished)
			return;

		if (_prevFastEma == 0m || _prevSlowEma == 0m)
		{
			_prevFastEma = fastEmaValue;
			_prevSlowEma = slowEmaValue;
			return;
		}

		if (_prevFastEma <= _prevSlowEma && fastEmaValue > slowEmaValue && Position <= 0)
		{
			BuyMarket();
		}
		else if (_prevFastEma >= _prevSlowEma && fastEmaValue < slowEmaValue && Position >= 0)
		{
			SellMarket();
		}

		_prevFastEma = fastEmaValue;
		_prevSlowEma = slowEmaValue;
	}
}