Fixed position but relative to container

Question

I am trying to fix a div so it always sticks to the top of the screen, using:

position: fixed;
top: 0px;
right: 0px;

However,

Answer 1

My project is .NET ASP Core 2 MVC Angular 4 template with Bootstrap 4. Adding "sticky-top" into main app component html (i.e. app.component.html) on the first row worked, as follows:

Is that the convention or did I oversimplify this?