protected override double CalcArea()
{
double A = 0;
for (int i = 0; i < _Vertices.Count; i++)
{
int j = IndexOfNextVertex(i);
A += ((_Vertices[j].X - _Vertices[i].X) * (_Vertices[j].Y + _Vertices[i].Y));
}
if (A < 0)
{
_Vertices.Reverse();
}
A = 0;
for (int i = 0; i < _Vertices.Count; i++)
{
int j = IndexOfNextVertex(i);
A += ((_Vertices[j].X - _Vertices[i].X) * (_Vertices[j].Y + _Vertices[i].Y));
}
return(1d / 2 * A);
}
