title: Why does my session variable appear to empty itself in ASP.NET?
body: <p>I have user control on a ASP.NET web page,  which contains a GridView  and a radio button selector. </p>
  
  <p>In the underlying middle tier I have a thread which goes to the database and then raises an event to say "I have some data" my User control handles this event and sets a Session Variable. </p>
  
  <p>This works and I can see the event being handled and the Session variable gets the new data. </p>
  
  <p>However when i go to use this session variable when the selected index of the Radio button selector changes the Session variable reports as "Nothing"</p>
  
  <p>I have ensured that the obvious (i.e. spelling, Sessions switched on etc) are correct. </p>
  
  <p>The GridView and radio button selector are encapsulated in the same Update panel. </p>