title: Error parsing AppSettings value with a query string
body: <p>In my AppSettings in <code>web.config</code>, I have something like this:</p>
  <pre><code>&lt;appSettings&gt;
      &lt;add key=&quot;ExternalSystemUrl&quot; value=&quot;http://example.com/page.aspx?id={0}&amp;action=eat&amp;object=bacon&quot; /&gt;
  &lt;/appSettings&gt;
  </code></pre>
  <p>However, it seems that when an ampersand (<code>&amp;</code>) is included in an AppSettings value, ASP.NET throws the following error:</p>
  <blockquote>
  <p>An error occurred while parsing EntityName</p>
  </blockquote>
  <p>Why does this happen, and how can I include URLs like this in <code>App.config</code>?</p>