Though its not clear what you want,but i think you mean Dropdown with autocomplete functionality. Right? If it is,
- Make normal JQuery AutoComplete
- Add image to right of the textbox so that it looks like dropdown
- Onclick of the textbox or image(Whatever your requirement is), add this
$(Element).autocomplete("search", "")
- set minLength attribute to 0 and you are done.
Have a look here :
Autocomplete Textbox in ASP.net[
^]
Regards..