There are several Server Event could trigger Method during item promotion: ItemType: OnBeforePromote, OnAfterPromote; Life Cycle: Transition Pre, Transition Post. Trigger sequence of above events is shown in below figure: It's important to note that "Transition Post" cannot rollback while exception throws because item promotion is finished after "OnAfterPromote" That means even if throwing exception, the life cycle will still stay at promoted state. Please note, all above events will not be triggered when "OnPromote" event exists (due to this will overwrite original system process).
Programming notes from a non-expert guy who keeps learning in various applications.