Event Receiver called multiple times

Question

I attached an event handler for ItemAdded to a content type A in the xml (using XmlDocuments). I have 4 other content types A1, A2, A3 and A4 that inherit from content type A (in their xml definition there is no event receiver defined). I create a custom list and add A1, A2, A3 and A4 to it.

When I add a new item to it through the UI, my event receiver is called once (as expected). When I add an item programmatically (see code below), my event receiver is called 4 times. Each time it is called, I noticed that the SPItemEventProperties.Context.ReceiverId changes. I've had a look at the EventReceivers table in SQLServer and noticed that there are four entries for my event receiver, all identical except for the ID of the event receiver and the Source ID (each have one of the four list content type's IDs). I think this is normal.

To programmatically add the item to the list, I do

SPListItem item = list.AddItem();
item[SPBuiltInFieldId.ContentTypeId] = <my list content type ID>;
...setting other fields...
item.Update();

Any idea why it works as expected when adding an item through the UI but not when adding through code?

Thanks

Answer 1

I recently got exactly the same problem, had about 20 content types i list, so event receiver was running 20 times when adding an item programmatically, even if it was registered only once in List.EventReceivers collection.

It also runs only once when adding an item through UI.

The workaround of setting ContentType field before updating the item works perfectly for me. Found it here

So try to set ContentType field instead of ContentTypeId in your code.

I don't know the reason behind that behavior, for me it feels like some kind of bug/feature in SharePoint. Maybe when user adds an item through UI, the code actually set all the field values presented in the form, including ContentType, so it does exactly the same thing as in workaround.

Answer 2

If you register the event receiver multiple times - it fires multiple time on update. Try this tool to see if the receiver is attached several times - http://speventreceiverman.codeplex.com/

Answer 3

Just to compliment Max's answer: I prefer using SharePoint Manager for checking Event Receivers.

You can even delete duplicate receivers from SPD.

Answer 4

Finally found it. In addition to the content type id, you also need to set the name of the content type:

listItem["ContentType"] = "MyContentTypeName";

I can't explain why it actually works though, I'd need to look at how the event receivers are resolved. I found the answer in the SaveButton webcontrol's source.