activeViewEvent.selectionChanged事件注册时报错

ArcObjects10.6，VS2017，Add-in
最后一句代码报错
System.InvalidOperationException:"event invocation for COM objects requires event to be attributed with DispldAttribute"，如何解决？

IApplication app = ArcMap.Application;

IMap map = (app.Document as IMxDocument).FocusMap;

IActiveViewEvents_Event activeViewEvent = map as IActiveViewEvents_Event;

activeViewEvent.SelectionChanged += activeViewEvent_SelectionChanged;

......