In this video Chris Pels shows how to create two DropDownList controls where selecting an item in the first list populates the items in the second list. First, an ASP.NET page is created with two DropDownList controls, one for customer and the other for states in which the customer does business. The customer list is then populated in the code behind. Next, in the SelectedIndexChanged event of the customer list the items in the state list are populated based upon the selection. Finally, there is a discussion of how this approach can be applied to other types of controls and data.