title: Implementing automatic logout in silverlight and wcf due to user inactivity
body: <p>I have a WCF web-service and a Silverlight app displaying data from that service. In my service I'd like to implement automatic logout of the user, if no service methods were invoked during a period of time (for example 20 minutes).</p>
  
  <p>I'm thinking about smth like that:</p>
  
  <pre><code>Dictionary&lt;User,TimeSpan&gt; Inactivity
  </code></pre>
  
  <p>When a service method is invoked i reset the TimeSpan. But what will happen, if 20 minutes pass, and I call the Logout method (which clears all User caches), and suddenly the User returns from lunch)) and presses a button in his Silverlight app? Obviously he'll get an error. Is there any way to avoid this, or all my concept is wrong? Maybe there's a better way to logout the user automatically?</p>