Convert listBox.SelectedItem to PointF

I have an item in my listbox;
I want to take it and convert it to PointF so that I can compare it with a list of pointF.

Example)
var selection = listBox3.SelectedItem ; // like "{X=18,Y=48.10001}"

PointF p1 = (PointF) selection;

//now when that item has been selected and converted to float point, I want to search and find it in list called optFlowPoints to see if that points exists

PointF drawPointEst=optFlowPonits.Find(p=>p.Equals(selection));

So there are two problems:

1. how to convert selectedItem to PointF


2. how to write my lambda expression to find the match

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