A frequent request for Revit add-ins performing time-consuming tasks is to display a progress bar. My own progress bar implementation is provided by the ADN MEP sample application AdnRme, originally dating way back to 2009 and earlier still. Now Limin He of FM:Systems encountered and resolved an issue with his progress bar in VB.NET, raising the following comment on the topic of the new exceptions raised by multithreading in Revit 2015: Question: We came across the same issue described above... Read more →