In itemupdating event
What if these documents were to require review and approval?Share Point as most us know, has built in workflow capabilities.
Therefore, you need to code defensively as the object you are expecting to be available in the Event Receiver may be null. So, in our situation, we check for this condition and return immediately when it is true.
For example ‘@Parameter’, will be sent in the update to the record instead of null.
To solve this, you would need to automatically detect whether a value is null and then add it to the Update Parameters list.
Even a simple app to enumerate the event receivers associated to the list only showed the one instance. Well, I had moved on to other things again, when all of a sudden, I noticed that new tasks were being created in the task list for some documents that I was uploading to a different document library. That’s pretty much the symptom for a receiver associated to a list template, but this was NOT a list template! It wasn’t going to show up in the Event Receivers collection for that list instance, because it was associated to the list type.
When I added it to the list instance, it just caused the event to fire twice on THAT list.
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The problem was that I had written an Event Receiver to handle Item Added events for a custom list.