RadComboBox supports a number of server-side events that let you respond to events with complex actions that can't be performed in client-side code.
ItemsRequested occurs when the load-on-demand mechanism needs to add items to the combobox.
ItemCreated occurs when a new item is added to the Items collection.
ItemDataBound occurs for each item when it is being bound to a data value.
SelectedIndexChanged occurs when the selected item has just changed.
TextChanged occurs when the text in the input area has been changed.
ItemChecked occurs when a checkbox is checked/unchecked.
CheckAllCheck occurs when the check all items check box is changed.
The SelectedIndexChanged , TextChanged and OnCheckAllCheck events do not fire unless you set the AutoPostBack property to True .