Charging barbarian

[Tapkill]

If I have unexpected strike as a rage power and am currently large so I have a threat range of 10ft. If someone charges me do i get my AoO before they hit me with their charge thus stopping the charge?

[Ryan. Costello]

A. You would get to make an AoO in this situation even without unexpected strike. Why wouldn't you with it?
B. Why would it stop the charge?

[daeran1]

You could try and trip the guy charging you with your AoO.