dbGeography如何检查点在多边形内部？

Question

我正在尝试在没有任何SQL数据库的情况下使用DbGeography。 我有1个多边形DbGeography和1个点DbGeography。

我尝试使用polygon.Intersects（point）来检查该点是否在多边形内，但Intersects始终返回true。

如何检查多边形内的点？

谢谢

编辑：

这是多边形

POLYGON((103.000833333333 14.2038888888889,103.000833333333 17.9880555555556,103.0675 18.1216666666667,103.300833333333 18.4216666666667,103.4175 18.4383333333333,103.9675 18.3216666666667,104.334444444444 17.8213888888889,104.784444444444 17.4047222222222,104.767777777778 16.6877777777778,105.001388888889 16.2544444444444,105.418055555556 16.0044444444444,105.634722222222 15.6708333333333,105.584722222222 15.0041666666667,105.534722222222 14.5538888888889,105.068055555556 14.2205555555556,104.467777777778 14.3538888888889,103.9175 14.3372222222222,103.3675 14.3538888888889,103.000833333333 14.2038888888889))

这是重点

POINT (98.9505555555556 18.7505555555556)

Answer 1

public void CheckInPolygon()
{
    bool inPolygon;

    PointF[] pts = new PointF[] { new PointF { X = 14.2038888888889f, Y = 103.000833333333f }, 
                                    new PointF { X = 17.9880555555556f, Y = 103.000833333333f }, 
                                    new PointF { X = 18.1216666666667f, Y = 103.0675f }, 
                                    new PointF { X = 18.4216666666667f, Y = 103.300833333333f } , 
                                    new PointF { X = 18.4383333333333f, Y = 103.4175f } , 
                                    new PointF { X = 18.3216666666667f, Y = 103.9675f } , 
                                    new PointF { X = 17.8213888888889f, Y = 104.334444444444f } , 
                                    new PointF { X = 17.4047222222222f, Y = 104.784444444444f } , 
                                    new PointF { X = 16.6877777777778f, Y = 104.767777777778f } , 
                                    new PointF { X = 16.2544444444444f, Y = 105.001388888889f } , 
                                    new PointF { X = 16.0044444444444f, Y = 105.418055555556f } , 
                                    new PointF { X = 15.6708333333333f, Y = 105.634722222222f } , 
                                    new PointF { X = 15.0041666666667f, Y = 105.584722222222f } , 
                                    new PointF { X = 14.5538888888889f, Y = 105.534722222222f }, 
                                    new PointF { X = 14.2205555555556f, Y = 105.068055555556f }, 
                                    new PointF { X = 14.3538888888889f, Y = 104.467777777778f }, 
                                    new PointF { X = 14.3372222222222f, Y = 103.9175f }, 
                                    new PointF { X = 14.3538888888889f, Y = 103.3675f }, 
                                    new PointF { X = 14.2038888888889f, Y = 103.000833333333f } };      //POLYGON as provided

    inPolygon = IsInPolygon(pts, new PointF { X = 18.7505555555556f, Y = 98.9505555555556f });          //POINT as provided

    MessageBox.Show(inPolygon.ToString());      //return : false
}

public static bool IsInPolygon(PointF[] poly, PointF point)
{
    var coef = poly.Skip(1).Select((p, i) =>
                                    (point.Y - poly[i].Y) * (p.X - poly[i].X)
                                  - (point.X - poly[i].X) * (p.Y - poly[i].Y))
                                .ToList();
    if (coef.Any(p => p == 0))
        return true;

    for (int i = 1; i < coef.Count(); i++)
    {
        if (coef[i] * coef[i - 1] < 0)
            return false;
    }
    return true;
}