index property in one item of customize collection

Question

hi, I want  to make a customize collection, and I want every item will have an Index property, such as ListViewItem has, which is unchangeable. Obviously I should be able to change that index from the collection class, so every item that is added will have the correct index. but how am i doing it?

thank you very much:)


edit: is that unclear? should I reexplain?