Pattern for Semi-Asynchronous Idling API Access

Here is another wonderful contribution from Daren Thomas: A Pattern for Asynchronously Updating Revit Documents ↗.

As an attentive reader of this blog, you will certainly remember one of my favourite and most powerful recent projects, the modeless loose connector navigator. It retrieves and displays a list of unconnected MEP connectors in a modeless dialogue box. Being modeless, the dialogue is not within the context of a Revit external command Execute method, nor any other Revit API call-back, and thus has no access to the Revit API, which does not permit asynchronous access. Happily, the Idling event provides a workaround for that.

The modeless loose connector navigator demonstrates a solution for handling a very specialised need, accessing the Revit API semi-asynchronously to highlight the elements with loose connectors.

Daren’s post generalises this solution, allowing a modeless dialogue to queue up a whole collection of actions to be taken, which can then be picked up and processed by the Idling event handler the next time it becomes active. A wonderful generic solution, including neat features such as:

• Use of the generic Queue template class.
• Use of the generic Action delegate, cf. 5. Generic Delegates ↗.
• Locking support to protect against simultaneous access to the queue from the modeless dialogue and the Idling event.
• Use of .NET => lambda statements to execute the queued-up tasks.

A truly beautiful job, Daren. Thank you!