Is there a model loaded event?

The organization diagram we are working on potentially has a lot of node in it and may takes a while to load. Is there an event that we can subscribe to know when the model.NodeSource is loaded so we can put a busy indicator when the model is loading? Apparently, model.NodeSource including loading the nodes from the data model plus layout the nodes so it takes a while to finish.

Try the Diagram.InitialLayoutCompleted event.