1  public static bool InsidePolygon(List<Point> polygon, Point p)
 2         {
 3             if (polygon.Count <= 0)
 4                 return false;
 5             int counter = 0;
 6             int i;
 7             double xinters;
 8             Point p1 = polygon[0], p2;
 9             int N = polygon.Count;
10 
11             for (i = 1; i <= N; i++)
12             {
13                 p2 = polygon[i % N];
14                 if (p1.Y != p2.Y && p.Y > Math.Min(p1.Y, p2.Y) && p.Y <= Math.Max(p1.Y, p2.Y) && p.X <= Math.Max(p1.X, p2.X))
15                 {
16                     if (p1.X == p2.X)
17                         counter++;
18                     else
19                     {
20                         xinters = (p.Y - p1.Y) * (p2.X - p1.X) / (p2.Y - p1.Y) + p1.X;
21                         if (p.X <= xinters)
22                             counter++;
23                     }
24                 }
25                 p1 = p2;
26             }
27             return (counter % 2) != 0;
28         }