What’s New in the Revit 2010 API: Events

The Event section of the API is one area that I believe developers have been hoping for years to see more… In 2010, Autodesk re-writes a bunch of what is there, adds a few more interesting events – but probably leaves out what you were hoping for…

Before and After

The biggest change, both for the re-written events and the new events is that they can receive callbacks either “before” the action or “after” – which is a very nice, mature feature for events. The “before” events enable you to either (1) fix the model before it is saved/printed/etc OR (2) stop the process and ask the user to do something before the action can be performed.

NOTE: for those of you who are thinking immediately about having “alternative interfaces” for something like Document.SaveAs – I think you’ll be disappointed. So far as I can see all of the “before” events are still fired after the user has completed the dialog (i.e. chosen the new SaveAs target file) – but before it actually happens.

User-Driven and API-Driven

I’m not sure that this was the case in the past – but there are notes with the 2010 release that indicate that the events will fire not just when triggered by interactive usage – but also when triggered by the API. I’m not 100% sure if I love that (once we developers all start using them at the same time) – but we’ll see.

Re-written Events

The following events have been re-implemented:
• Document Creation
• Document Opening
• Document Saving
• Document Save As
• Document Closing
• DialogBox showing (Revit 2010 generally uses the newer style “TaskDialog” from WPF, rather than the old-school “MessageBox” of the last 15 years)

The New Events

The new events are:
• File Export
• File Import
• View Printing
• Document Printing
• View Activating
• Document Save to Central

The last one, saving a document to the central file – has some interesting options – including being able to see the exact properties that have been used for the operation, including:

• Compact Central File
• Relinquish Borrowed Elements
• Relinquish Family Worksets
• Relinquish Project Standard Worksets
• Relinquish User Created Worksets
• Save Local File

That said, alas, they are read-only.

In Summary
I know you were hoping for an element-level event. Autodesk knows that you’d like to have it – but there are apparently some complexities and pitfalls to giving us this power (not the least of which is that we could probably cause never-ending cascading update loops).
All in all, though – the events took a good step forward in terms of the maturity of the API. They’re better thought out than before, and they’ll get more usage.