Question

Tell me please, why this sample code doesn’t work on ASP.NET MVC?

http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.listcontrol.onselectedindexchanged.aspx

Thank you

Answer 1

That code does not work, because asp.net mvc does not have knowledge of controls, used in asp.net webforms (ListControl is one of those controls). WebForms controls rely on ViewState and javascripts generated by webforms framework. Asp.net mvc has no concept of viewstate, neither does it generate any default javascript for page.

If you want to trigger action from client side in asp.net mvc, you could write pure html and javascript(using jquery for simplicity). 
In controller

//action to invoke dynamically
public ActionResult GetSomeData(int id)
{
   return Content("id is " + id);
}

And in view

<select id="myselect">
     <option value="1">One</option>
     <option value="2">Two</option>
</select>
<script>
   $(function(){
      $('#mySelect').change(function(){
          $.get('@Url.Action("GetSomeData")', {id: $(this).val()}, function(data) {
              alert(data);
          });
      });
   });
</script>

This should alert ‘id is 1’ and ‘id is 2’ accordingly.