I learned something today
You can render a method obsolete like this
/// An obsolete method in a class far, far away.
[SysObsoleteAttribute('This is the error message you will see when you compile code that callse this method even though it is obsolete.', true)]
public void obsoleteMethod()
Now when you try to compile code that calls this method, you will see:
I don’t care what you say. I think it’s pretty cool.