title: How to use ASP.Net server controls inside of Substitution control?
body: <p>while the method we use in Substitution control should return strings, so how is it possible to use a <a href="http://weblogs.asp.net/scottgu/archive/2006/11/28/tip-trick-implement-donut-caching-with-the-asp-net-2-0-output-cache-substitution-feature.aspx" rel="noreferrer">donut caching</a> in web forms on a server control which should be rendered server side?<br>
  for example Loginview control?</p>