title: Losing the session after the Postback
body: <p>I have been using session variables in my asp.net application for passing the next property:</p>
  
  <pre><code>[DefaultValue(true)]
  public bool IsModificationMode
  {
      get
      {
          return (bool)Session["ModificationMode"];
      }
      set { Session["ModificationMode"] = value; }
  }
  </code></pre>
  
  <p>In the PageLoad, I set it's value.</p>
  
  <p>Now after the Postback, I am losing it's value having a a NullReferenceException</p>