The server-side OnDropDownSelectedIndexChanged event occurs when the user clicks on item in the DropDown, causing a postback.
The event handler function receives two arguments:
The RadRibbonBar which has fired the event. This argument is of type object, but can be cast to the RadRibbonBar type.
An EventArgs object.This object has a number of properties for handling the request for the items:
Index – index of the newly selected item.
Item – the newly selected item.
DropDown – the DropDown which fired the event.
Group – the group in which the DropDown is placed.