dropdownlist with country,state binding

Hi friends,

 I am doing asp.net online project for school. In that I have three field 1.Country 2.state,3.city. i am using dropdownlist for country, state.my question is if i bind all country then i need to bind all state for corresponding country.I think this is difficult to get state for all country. so please tell me how can i do it simple or is any easy way to do this task.