title: How to change in runtime application settings
body: <p>I'm trying to change in runtime one key of my applications settings file, but it does not work.</p>
  
  <p>I do on that way:</p>
  
  <pre><code>ConfigurationSettings.AppSettings["XPTO"] = "HELLO";
  </code></pre>
  
  <p>It seems that it only changes in memory, not on the file.</p>
  
  <p>Does anyone knows how to do this?</p>
  
  <p>Thanks.</p>