I took a quick peek at this and as far as I can tell it seems you can only go in the direction of .NET --> LabVIEW. In other words you can register a VI to be called when an event is fired by a .NET control, but you can't register .NET to handle a LabVIEW event. I suppose you could just use the LabVIEW event handler to simply call the .NET assembly when the LabVIEW event happens as a "manual" solution.