Itemupdating not firing

Whenever we work with Event Receiver or Remote Event Receiver in Share Point, we come across two common methods that are automatically created when we add an event receiver *file.These methods are - Both the methods are always confusing with respect to their usage.Do I have to call the Change Mode() method in the Mode Changing event handler? I can see the mode in the process of changing, because my Mode Changing handler gets called, but then the Mode Changed handler never gets called. I didn't think to check whether Mode Changed was only called when using a Data Source ID-object.

So, here is the basic difference between them by which one can get the clear basic idea of them both, hence, selecting the required one between them to write their business logic codes.

Remote Event Receivers are a powerful way to integrate custom code into your Share Point Online environment.

Essentially a Remote Event Receiver is a hook that allows you to execute your code in response to an event that occurs in Share Point.

It is also very easy to attach, develop, deploy, test, and maintain. Remote Event Receivers were introduced along with Share Point 2013 and the arrival of the App model.

Microsoft provided tooling with Visual Studio to create Remote Event Receivers, but unfortunately the only way to expose this tooling was in the context of a Provider-Hosted App.