Filtering records from 1st combobox to 2nd combobox and 2nd to 3rd combobox

Question

i have 3 forms in my C# application. in 1st form "country combo". 2nd form "state combo" in 3rd form "district combo". i want to filter record from 1st combo to 2nd and 2nd to 3rd combo. like i select country "india" in 1st combo. then in 2nd combo it's corresponding "state" should display. after selecting state in 3rd combo it's corresponding "district" is display