Would it be wwwroot, C, the root virtual directory where the assets are hosted, or the same folder that the assets are in?
Meaning if I have a virtual directory 'virdir' with a sub directory 'swf', which is really like C:\somedir\assets\swf\, where would the crossdomain.xml need to go so that my swf app on a different server can access the swfs?
you need to be able to access it as http://yoursite.com/crossdomain.xml so where would you put it to do that?
As a rule of thumb I put it next to my index.html for the site.
wwwroot will likely work for you.
来源：https://stackoverflow.com/questions/213389/when-it-says-put-crossdomain-xml-in-the-root-where-would-that-be-on-iis