Hi,
During the development of my payment plugin, i wanted to display a Succes or Error notification after saving the plugin settings, like Nop does when saving all the other settings (after you click save a notification text is displayed under the admin menu).
But after looking in the code I discovered that the ErrorNotification and SuccessNotification methods are available in the BaseNopController.
This is why they cannot be used in a plugin, because (in my case) it's using the BaseNopPaymentController, which doesn't have these methods.
I nice solution will be a "CommonBaseAdminController" as the base controller for the BaseNopController and all the plugins base controllers and move the Success and Error methods in there (and maybe other common stuff needed in the future).