I am implementing the autocomplete feature on RADComboBox. I would like to know what event is called for doing autocomplete and also can i override the inbuilt autocomplete search functionality
When you try to autocomplete an item inside of the input area of RadComboBox the SelectedIndexChanged server event is fired. The event's second argument (RadComboBoxSelectedIndexChangedEventArgs) holds information about the currently selected item as well as the previously selected one.
You could also consider handling the onclientitemsrequesting event to do custom processing via JavaScript as demonstrated in this documentation page.
Can you be more specific about the functionality that you want to implement?