When the application is idle, the library makes a series of calls to allow controls to update their associated actions so that they reflect the current properties of the controls. The first of these is to the InitiateAction method of the each form, followed by the InitiateAction methods of its visible menus and controls. 

InitiateAction calls the action's update method indirectly (through its action link), which leads to a number of events, any of which may update the action and stop the update process: 

1.First, the action list that contains the action receives an OnUpdate event.  

2.If the action list does not handle the OnUpdate event, then the Application object receives an OnActionUpdate event.  

3.If the OnActionUpdate event handler does not update the action, the action itself receives an OnUpdate event.  

4.If that does not update the action, the active control's UpdateAction method is called. 

5. Finally, if the action is still not updated, the active form's UpdateAction method is called.

OnActionUpdate 

Action 

ActionLink 

UpdateAction 

OnUpdate 

OnUpdate 

Update