title: jquery cascade dropdownlist will clear after postback
body: <p>I have made a cascade dropdown list using jquery and ajax, the first dropdown shows states and the second one shows cities according to selected state.
  when a postback occurs I can get selected city with this code:</p>
  
  <pre><code>Request.Form[DpCity.UniqueID];
  </code></pre>
  
  <p>but the city list will clear. how can I retain the city list values during postback something like using view state?</p>