Differences between ItemizedOverlay and Overlay class

Question

Can someone tell my when to use Overlay or when to use ItemizedOverlay class!

What are differences between this two classes?

Draw methods do the same thing?

Answer 1

Overlay is a general overlay. ItemizedOverlay is a subclass that makes it easier to create an overlay that is a discrete series of marked points on the map. So, if you are trying to show a bus route, or shade a region, or something like that, Overlay is the class you want. If you are trying to show a collection of restaurants, or churches, or whatever, ItemizedOverlay works.

Note, though, that ItemizedOverlay is designed for modest numbers of points (e.g., dozens). If you have a large number of points, you may need to create your own Overlay just for performance reasons.