Item updated via CSOM will not fire remote event receiver

Question

We have a remote event receiver associated to a list and hooked on all events there. When you update any list item using OOB SharePoint page, the event receiver is executed; a web service which is taking care of the afterward actions works nicely. However when you update item use CSOM code e.g. in simple console application, nothing happens. The event receiver is not called at all. I found this issue on both SP 2013 and 2016.

I will not post any code while it is irrelevant: item is updated using standard approach and values are actually changed in the list item, only the event receiver is not fired. To put it simply: item updated manually from site -> event receiver fired item updated via CSOM -> event receiver not fired.

I remember similar issue on SharePoint 2010 when using server side code and system account. Could it be that behind the scene web service called by CSOM (e.g. list.asmx) is using system account to make changes as well? It's just hypothesis...

Answer 1

So after deeper investigation and many try/fails we found out it was indeed issue with code in our event receiver. For some strange reason original developers were checking Title field in after properties and cancelling code if not present. I guess it was probably an attempt to prevent looping calls.

One lesson learned: When using CSOM after event properties contains only those fields which were altered by CSOM code. Keep it in a mind in case you need to use other values than those you want to update. You may need to stupidly copy and assign them again just because of this.