When Undo will not Undo

Every now and then, Revit will remove everything from the list of things you can Undo.

It's called 'flushing the undo stack'.

Various things trigger this scary behaviour:

• Making a Workset editable WITHOUT using the Worksets dialog box
• Deleting a View, from a workshared project that is not 'checked out' (editable, see first point)
• Deleting a Family via the Project Browser, from a workshared project where the Family is not 'checked out' (editable, see first point)

An interesting workaround - if you check out the View workset manually (using the Workset dialog), and THEN Delete it, you can still Undo from this point.

This leads to some seriously scary possibilities - if you plan to delete a view with a 1000 detail lines and text elements, make extra-certain first!