how can I locate site web.config in an IIS virtual folder instead of site root
<p>I have multiple instances of an ASP.NET web application that are identical in every way except for the web.config file, which contains the instance-specific settings.  In order to avoid having multiple copies of the same set of files, I want to place all or part of the web.config file in an <strong>IIS</strong> virtual folder.  </p>

<p>I created an IIS virtual folder "config" under the site root folder and used the following line in the web.config file to refer to it:</p>

<pre><code>&lt;appSettings configSource="config\\app.config" /&gt;
</code></pre>

<p>Unfortunately, IIS looks for a physical path under the site root folder named "config", and coughs up an error when it can't find it.</p>

<p>Does anyone know a way to trick IIS into using the <strong>IIS</strong> virtual folder? I am also open any suggestions (including server-side code) on how to accomplish the same goal (using the same folder to serve multiple instances of the same web site differing only by appSettings).</p>

<p>I have also considered dumping all the content into a virtual "web" folder, but this would require re-basing all references in nearly 200 files.  Using the  tag is not a viable solution here because it re-bases everything including same page references, yet inexplicably does not work for references to .less files.</p>

<p><em>Edit: while the idea is to use the same folder for multiple instances, I want to make it clear that each instance would be set up in IIS as a separate web site/application.  It's just that each instance would point to the same physical folder.</em></p>