public class MyLineSeries : LineSeries
{

    List<ScreenPoint> outputBuffer = null;

    public bool Aliased { get; set; } = true;

    protected override void RenderLine(IRenderContext rc, OxyRect clippingRect, IList<ScreenPoint> pointsToRender)
    {
        var dashArray = this.ActualDashArray;

        if (this.outputBuffer == null) 
        {
            this.outputBuffer = new List<ScreenPoint>(pointsToRender.Count);
        }

        rc.DrawClippedLine(clippingRect,
                           pointsToRender,
                           this.MinimumSegmentLength * this.MinimumSegmentLength,
                           this.GetSelectableColor(this.ActualColor),
                           this.StrokeThickness,
                           dashArray,
                           this.LineJoin,
                           this.Aliased,  // <-- this is the issue
                           this.outputBuffer);

    }
}