I have problems with sharing files from this directory. It is system
directory so I can't make dirrect links on files inside. For example
/App_Data/my.mp3
www.example.com/App_Data/my.mp3 - forbidden link

I have tring make a handker which should read this file and write to response
www.example.com/file.ashx?filename=my.mp3
But I have other problem with it. It can be different file and for any of
this I need  to know
1) which Mime Content Type for this and
2) when it save it save with name of handler file file.ashx but it should be
my.mp3

So how I should make http links on files from App_Data.

ps. I use this App_Data folder for save my files only because it allow
create/remove directories without errors. If I remove some other folder
inside site - page as usual freezing