You just need to make an AJAX call and take the search results then send them back as JSON to the client side.Then just bind it with the AutoComplete Textbox.
The jQuery plgin to be used is http://docs.jquery.com/UI/API/1.8/Autocomplete
Example- A textbox with ID 'txtlocation' is added with autocomplete functionality here.
$(document).ready(function(){
$("#txtlocation").autocomplete({
source: function (request, response) {
$.ajax({
url: "/PublicHome/AutoPopulateLocation", //Call to Server Side
data: "{ 'searchText': '" + request.term + "' }",
dataType: "json",
type: "POST",
contentType: "application/json; charset=utf-8",
dataFilter: function (data) { return data; },
success: function (data) {
response($.map(data, function (item) {
return {
value: item.Suburb
}))
},
error: function (XMLHttpRequest, textStatus, errorThrown) {
}
});
},
open: function (event, ui) {
$(this).autocomplete("widget").css({
"width": 344,
"font-size": 11,
"font-family": "Arial"
});
}
});
});