How to find the boundary of close points in .net?

Question

I have many points and I can draw it in a image. there will be many many points .

what I want is to find the points is closely.

and may be there will be two closely points area.

remove the unclose point is what i need.

List<PointF> MyPoints{get;set;}

1.I set a distancePer=0.5f; and get all the average * distancePer of the points distance and remove the points which is too far from which is near to it.

2.I draw them in a image and use opencv to get the near points.

two of them both not work.

thank you.

What I want to do is to find a closely points groups.

let me explain.

some points are loosely in the picture and what I want to do is to remove the loosely points. only left the un-loose points. which is small distance to the groups.

it is like a backterial colony I want to remove the far distance points.