In itemupdating event
Removal of an add-in only moves the add-in to the user's recycle bin.Two more steps are required before the App Uninstalling event is triggered.The infrastructure will rerun the event, , up to three additional times.After four timeouts, Share Point will roll back the entire add-in installation.First, a user must remove the add-in from the recycle bin, which moves it to the second stage recycle bin.Second, a user must remove the add-in from the second stage recycle bin.When you are working in Visual Studio, and you add a RER to a Share Point Add-in project, the Office Developer Tools for Visual Studio do the following: When a registered event occurs, Share Point calls the appropriate method in your service and passes an object that provides some context information for your code.For example, the event type (from one of the two tables earlier in the article) is identified, so that your code can branch to the logic that is appropriate for the event.
There are two kinds of events: To handle list and list item events, you create remote event receivers (RERs), which are web services that run externally to the Share Point farm or Share Point Online.
The full implications of these facts are discussed in Include rollback logic and "already done" logic in your add-in event handlers.
The App Uninstalling event does run when the add-in is removed from the host web.
The add-in is visible in multiple web sites in the tenancy, but the event does not run separately for each of these.
Besides canceling an add-in installation, this event can be used for many other purposes including: Important Your implementation of the App Installed event must complete within 30 seconds or the Share Point installation infrastructure will think it has failed.