title: Web service - cache update
body: <p>I am trying to make a web service that caches its output content. </p>
  
  <p>I have added <code>[WebMethod(CacheDuration=1800)]</code>, but the problem is that i want the web service to update its cache automatically after, say 30 min, without any requests to it. </p>
  
  <p>I am using .net with C#. the web service is actually a proxy that gets xml data, parses it and sends it to the client.</p>
  
  <p>How can the web service update its cache after some time period (by itself)?</p>