I have multiple websites that all have the same code, but different app settings. I want to place my app settings in a separate configuration file that is located in a virtual directory. This will allow me to have a single copy of all of the code shared across all of the sites with a different virtual directory for each site.
Unfortunately, when I try to configure this, IIS doesn't process the config file when it is in a virtual directory.
If you have a solution to this, I would appreciate your help.
Maybe using the machine.config file on your web server would be a suitable alternative? Otherwise you could create a web.config file in a global folder somewhere and open it using the WebConfigurationManager.OpenMappedWebConfiguration() method.
It's not possible to use a virtual directory (or even files outside of the current website; only the current folder, or a sub-folder).
One possible way to share setting across projects would be to do it at build-time - either by coping it in, or using a Linked File in VS to have it copied to the folder on publish.
If you really need this functionality on the server, you could try (though I can't say how well it would work) a Junction.
来源：https://stackoverflow.com/questions/587537/iis-config-file-in-virtual-directory