Derived classes can choose what data and type to store in this indexer. Typically this is implemented as a WeakEventManager.ListenerList, which is a list of weak references to listeners. You would only have to change this type if the WeakEventManager.ListenerList type cannot contain your required information. If so, you will have to override the Purge method so that all cleanup of the underlying type is performed correctly.
Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)