For Biding Your Dropdown you can use this..
1) Declare a webmethod in your codebehind page that will work for binding your dropdown
2) and at the time of page load you can call that method using jquery + ajax call back
3) so that work silently and your page is loaded faster.
and you can also use a lazy loading
Refrance for Lazy Loading
ASP.NET Lazy Content Loading Through WCF REST Service