Invoke Ribbon button in Outlook 2013
问题 We have an Outlook add-in. We need to programmatically cancel a task assignment in the TaskItem Inspector window, just the way the Cancel Assignment button does. One would think that calling TaskItem.CancelResponseState() might work. Although it does cancel the assignment, it also leaves the task in an unassignable state. The Assign Task button on the ribbon is disabled. In Outlook 2007 and 2010, we can get the CommandBarButton object for the Cancel Assignment button and call its Execute()