Implement jQuery AutoComplete TextBox in Content Page in ASP.Net

Hey, I need your help.

I need to create a GridView, using C# and ASP.Net, that populates from a TextBox (AutoComplete TextBox) that autocompletes (autocomplete extender) from database data.

I have tried this demo without success.

https://www.aspsnippets.com/demos/2899/ Can you help me?

Thanks

<%@ Page Title=""
    Language="C#"
    MasterPageFile="MaP.master"
    AutoEventWireup="true"
    CodeFile="Default.aspx.cs"
    Inherits="_Default"
    EnableEventValidation="false"
    MaintainScrollPositionOnPostback="true" %>

<%@ MasterType VirtualPath="MaP.master" %>
<%@ Register TagPrefix="asp" Namespace="AjaxControlToolkit" Assembly="AjaxControlToolkit" %>
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="ajax" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="Server">
    <script type="text/javascript">

        $(function () {
            $(".Country").autocomplete({
                source: function (request, response) {
                    $.ajax({
                        url: 'Default.aspx/GetCountries',
                        data: "{ 'prefix': '" + request.term + "'}",
                        dataType: "json",
                        type: "POST",
                        contentType: "application/json; charset=utf-8",
                        success: function (data) {
                            response($.map(data.d, function (item) {
                                return {
                                    label: item.split('-')[0],
                                    val: item.split('-')[1]
                                }
                            }))
                        },
                        error: function (response) {
                            alert(response.responseText);
                        },
                        failure: function (response) {
                            alert(response.responseText);
                        }
                    });
                },
                select: function (e, i) {
                    $(this).parent().find("input[type=hidden]").val(i.item.val);
                },
                minLength: 1
            }).focus(function () {
                $(this).autocomplete("search");
            });
        });
    </script>

    <script src="https://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.10.0.min.js" type="text/javascript"></script>
    <script src="https://ajax.aspnetcdn.com/ajax/jquery.ui/1.9.2/jquery-ui.min.js" type="text/javascript"></script>
    <link href="https://ajax.aspnetcdn.com/ajax/jquery.ui/1.9.2/themes/blitzer/jquery-ui.css" rel="Stylesheet" type="text/css" />
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder2" runat="Server">
   <asp:TextBox ID="txtCountry" runat="server" CssClass="Country" />
   <asp:HiddenField ID="hfCountry" runat="server" />
</asp:Content>