Well, I guess that's a matter of philosophical attitude.  Personally, I  
feel that simply being "so basic" isn't a sufficient condition for  
inclusion in a framework (.NET or otherwise).  It's not even a _necessary_  
condition.

The framework needs to include things that are _common_ usage.  In some  
areas, it would of course include some less-commonly-used options to allow  
customization of behavior.  But even there, I would say those options  
would generally be things that can apply more broadly (so would have more  
common usage overall) or would not otherwise be easily reproduced (so  
without which a given "commonly used" component might wind up useless).

This particular example doesn't fall into any of those categories.  It  
really is trivial to implement a timed dialog box, and it's definitely not  
something that would be commonly used (in fact, while you say "windows  
uses it in some of its apps already", I have to say that I can think of  
only one such example off the top of my head -- the "End Task" dialog --  
and there's no indication to me at all that the behavior is actually in  
the Windows API itself, rather than having been implemented as a one-time  
feature for that one dialog).

I wouldn't be so bold as to say this sort of thing would never be in .NET,  
but it's absolutely not the kind of thing that I'm surprised or  
disappointed hasn't been included in .NET so far.

Pete

A message box has the responsibility of alerting the user and ensuring that
they acknowledge the message.

A message that pops up and dismisses itself after a period of time is a
tooltip.