Try this:
$(document).ready(function () {
$('#Ddl').change(function () {
var $this=$(this).find(":selected");
var text=$this.text();
var value=$this.val();
});
});
However, if it is an Asp.Net web form, you need to change the
Dbl
to
<%= Dbl.ClientID %>
due to the dynamic handling of client id by the .net framework.