title: What is the difference between Page.IsPostBack and Page.IsCallBack?
body: <p>I've recently ran into some code that checks <code>Page.IsCallBack</code> but I wasn't sure how it is different from <code>Page.IsPostBack</code>. Can anyone enlighten me?</p>
  
  <p><strong>Edit</strong>: Are they mutually exclusive or can both occur at the same time in a given situation?</p>