RadComboBox provides a rich and easy-to-use server side API, so you can easily populate your combobox with any number and or type of items. Each combobox instance (RadComboBox) exposes the Items collection (RadComboBoxItemCollection) which in turn may hold any number of Items (RadComboBoxItem) with different properties / settings. All methods/properties for dealing with ComboBox, Items and Collections are intuitive and follow ASP.NET conventions.