*"I would implement an algorithm which would check if the point is inside or outside or exactly on border of the polygon."*

In Euclidean geometry in two dimensional space a point will only have these three options you mentioned so rest assured that regardless of the passed parameters all you have to do is

`return true;`

.Cheers!

But you don't bother to cite it, and, you don't even have the input parameters written correctly: "poly" has got to be a List<Point> in your case.

Get to work.