create dynamic control using c# in asp

Question

How can i create a set of dynamic control in asp platform with using c#.

i have a label and a dropdownlist... 

first i make selection from the dropdownlist, then i want a label and dropdownlist create and the choice of the combo will query from db based on the dropdownlist1 text.

it will keep looping until the last level. which means from the second selection, it will create a 3rd set of label and combo where choices are based on the dropdownlist2 text searching from db.