Tip: Set the SelectedValue on a DropDownList that is populated by a CascadingDropDown

When using a DropDownList, you can set the selected item by using the SelectedIndex property. However, if your DropDownList is being populated by the CascadingDropDown control (from the ASP.NET AJAX Control Toolkit), that doesn’t work. Instead, you must use the SelectedValue property on the CascadingDropDown control.