Registers an ASP.NET server control as one requiring an event to be raised when the control is processed on the System.Web.UI.Page object.
Only one server control can be registered per page request. The Page.RegisterRequiresRaiseEvent(IPostBackEventHandler) must be used when the control does not include its control ID in the form post data. Also, the control that is registered must implement the System.Web.UI.IPostBackEventHandler interface.