how to make autocomplete dropdown/textbox in mvc

$('#<%=txtsearch.ClientID%>').autocomplete({
source: function (request, response) {
var s = document.getElementById('<%=txtsearch.ClientID%>').value
$.ajax({
url: "Default.aspx/GetAllCities",
dataType: "json",
data: "{'prefixText': '" + s + "'}",
contentType: "application/json; charset=utf-8",
type: "POST",
dataFilter: function (data) {
return data;
},
success: function (data) {
if (data.d.split(',').length > 9) {
$(".ui-autocomplete").css("height", "200px");
}
else {
$(".ui-autocomplete").css("height", "auto");
}
response(data.d.split(','));
},
});
},

select: function (e, ui) {
var sname = ui.item.value;
}
});