c# - I need a notification system in a web application -

I have a web application that our customers use it all day. Sometimes, I have to stop or restart the application . When I do this, the work of some customers is interrupted and it makes them nervous.

I want to create a notification system which appears on the application and informs the customers about the system's closure.

How do I create a system like this?

You can use the notification

You also customize the error page Can "HTTP Error 500-12 Restart Application"