PolyBLEP waveform implementation in C#

Osc.cs

public static class Oscillator
{
    public static double EvaluateSaw(ref double phase, double phaseInc)
    {
        double value = SampleSaw(phase) - PolyBLEP(phase, phaseInc);
        
        phase += phaseInc;
        phase %= 1.0;
        
        return value;
    }
    
    public static double EvaluateSquare(ref double phase, double dutyCycle, double phaseInc)
    {
        double value = SampleSquare(phase, dutyCycle)
            + PolyBLEP(phase, phaseInc)
            - PolyBLEP((phase + (1.0 - dutyCycle)) % 1.0, phaseInc);

        phase += phaseInc;
        phase %= 1.0;
        
        return value;
    }

    private static double PolyBLEP(double t, double dt)
    {
        // 0 <= t < 1
        if (t < dt)
        {
            t /= dt;
            return t+t - t*t - 1.0;
        }
        // -1 < t < 0
        else if (t > 1.0 - dt)
        {
            t = (t - 1.0) / dt;
            return t*t + t+t + 1.0;
        }
        
        // 0 otherwise
        return 0.0;
    }

    private static double SampleSaw(double phase)
    {
        return (2.0 * phase) - 1.0;
    }
    
    private static double SampleSquare(double phase, double dutyCycle)
    {
        return phase < dutyCycle ? 1.0 : -1.0;
    }
}