title: Forms Authentication adding additional information along with ReturnUrl
body: <p>With Forms Authentication when the app needs to redirect to sign-in page is there an event or any extensibility point that will let me do additional work to the request before it redirects to the sign-in page?</p>
  
  <p>I would like to send additional information in the query string that could vary such that it wouldn't work to just statically embed that in the link in the loginUrl node in the web.config.</p>
  
  <p><strong>Edit:</strong> For clarification, I want to intercept the request prior to being redirected <strong>TO the login</strong> page.</p>
  
  <p><strong>Example:</strong></p>
  
  <pre><code>&lt;authentication mode="Forms"&gt;
        &lt;forms loginUrl="http://the/interwebs/login.aspx" timeout="2880" 
                  enableCrossAppRedirects="true" /&gt;
  &lt;/authentication&gt;
  </code></pre>
  
  <p>And prior the user being redirected to <a href="http://the/interwebs/login.aspx" rel="nofollow">http://the/interwebs/login.aspx</a> I would like to be able to pack in query values so the url could end up something like <a href="http://the/interwebs/login.aspx?Action=Refresh" rel="nofollow">http://the/interwebs/login.aspx?Action=Refresh</a></p>