Stopping an ASP.NET site with only FTP access

I recently needed to stop an ASP.NET web applications so that I could upload a new version of some pages. I only had FTP access, which couldn't overwrite the files because they were in use (by the web server process). Fortunately, there is a way to shut down dynamic ASP.NET requests with just FTP. Placing a file named App_Offline.htm in the site root will cause new requests to be blocked, while existing ones will continue. Once they all finish, it should be possible to update the ASP.NET page files. Removing App_Offline.htm will bring the site back to normal.