Recently I was tasked with writing an event-handler that basically increments a unique number and assigns this to the ‘Document Number’ list item in a document library once a document is added.

Sounds reasonable yes? Usually it is simply a case of adding code to the itemAdded / ItemAdding or ItemUpdate / ItemUpdating events of the list, getting a new number and assigning it to the ‘document number’ column in the list.

The problem is when Check in & Checkout is enabled on the document library. When this is enabled, a lot of strange and wonderful things happen, specifically in regard to how the events fire. I’ve basically debugged the sequence and it’s shown below:

Standard Document Library, no Check In or Check Out turned on.

New document from the ‘New’ menu item

• ItemAdding
• ItemAdded

Saving document using the same name as an existing document

• ItemUpdating
• ItemUpdated

Uploading a new document using the ‘upload’ menu item

• ItemUpdating
• ItemUpdated
• (Prompted user for document properties)
• ItemUpdating
• ItemUpdated

Multiple uploads. 1 new document, 1 existing. NB, No Doc Properties window is shown during the upload.

• ItemUpdating
• ItemUpdated
• ItemAdding
• ItemAdded

Multiple uploads, 2 existing documents in the document library

• ItemUpdating
• ItemUpdating
• ItemUpdated
• ItemUpdated

Now lets turn on Check In and Check Out on the document library.

Check In turned on. New document

• ItemAdding
• ItemAdded
• ItemCheckingOut
• ItemCheckedOut
• At this point your prompted to check in.
• ItemUpdating
• ItemUpdated
• ItemUpdating
• ItemCheckingIn
• ItemUpdated
• ItemCheckedIn

New document, Check In turned on, but user didn’t check in the document.

• ItemAdding
• ItemAdded
• ItemCheckingOut
• ItemCheckedOut

User proceeds to check in the document that was added in the previous step.

• ItemUpdating
• ItemUpdated
• ItemUpdating
• ItemCheckingIn
• ItemUpdated
• ItemCheckedIn

Upload single document

• ItemAdding
• ItemAdded
• Prompted for doc properties!
• ItemUpdating
• ItemUpdating
• ItemUpdated
• ItemCheckingIn
• ItemUpdated

2 new documents uploaded

• ItemAdding
• ItemAdding
• ItemAdded
• ItemAdded

2 documents uploaded in previous step. Need checked in. Events fire once per document.

• ItemUpdating
• ItemCheckingIn
• ItemUpdated
• ItemCheckedIn

1 document dragged in from Explorer View

• ItemAdding
• ItemAdded

Multiple documents dragged in from Explorer View

• ItemAdding – doc1
• ItemAdded
• ItemAdding – doc2
• ItemAdded

Checking in Explorer Documents from previous step (runs per document)

• ItemUpdating
• ItemCheckingIn
• ItemUpdated
• ItemCheckedIn

So what’s the bottom line? Ultimately the event handler should be tailored to determine if Check In/Checkout is enabled. If Check In/ Check Out isn’t enabled, use Adding/Added/Updating/Updated. If it is, use the Checked In handler. I haven’t come across a technique to determine through the properties item if check in is turned on. I suspect I’d have to access the list and go from there.