title: Access specific appsettings key in Url Rewrite rules
body: <p>I am trying to access AppSettings Key in the Url Rewrite rules and I am not sure how to access them. Can anyone help me out?</p>
  
  <pre><code>&lt;appSettings&gt;
    &lt;add key="APIUrl" value="https://www.x.com/api/{R:1}" /&gt;
  &lt;/appSettings&gt;
  &lt;system.webServer&gt;  
   &lt;rewrite&gt;
    &lt;rules&gt;
      &lt;rule name="ProxyApi" stopProcessing="true"&gt;
        &lt;match url="^api/?(.*)" /&gt;
        &lt;serverVariables&gt;
          &lt;set name="HTTP_X_ORIGINAL_ACCEPT_ENCODING" value="{HTTP_ACCEPT_ENCODING}" /&gt;
          &lt;set name="HTTP_X_ORIGINAL_HOST" value="{HTTP_HOST}" /&gt;
        &lt;/serverVariables&gt;
        &lt;action type="Rewrite" url="{APIUrl}" /&gt;
      &lt;/rule&gt;
    &lt;/rules&gt;
   &lt;/rewrite&gt;
  &lt;/system.webServer&gt;
  </code></pre>
  
  <p>Trying to access the APIUrl key in the UrlRewrite Rule</p>