How to get all objects and how to determine the shortest distance between objects?

Question

AutoCAD

I wrote everything in the question.
I can't figure out how to get all objects in a layer and how to determine the shortest distance between some objects?
How to get objects found here

Answer 1

Let's talk about geometry...

public static float Distance(PointF one, PointF two)
{
    return (float)Math.Sqrt(Math.Pow(Math.Abs(two.X - one.X), 2) + Math.Pow(Math.Abs(two.Y - one.Y), 2));
}