Why highchart not show me in asp.net? - asp.net

Question

I'm beginner in asp.net and highchart control,want to use highchart control in my web application web form,for that purpose read this tutorial:
this tutorial
and write this web service in my project:
public class cityPopulation
{
public string city_name { get; set; }
public int population { get; set; }
public string id { get; set; }
}
[WebMethod]
public List<cityPopulation> getCityPopulation(List<string> pData)
{
List<cityPopulation> p = new List<cityPopulation>();
cityPopulation cpData = new cityPopulation();
cpData.city_name = "tabriz";
cpData.population = 100;
p.Add(cpData);
return p;
}
that web service name is this:
WebService1.asmx
and in my web form write this script :
<script type="text/javascript">
function drawPieChart(seriesData) {
$('#container').highcharts({
chart: {
plotBackgroundColor: null,
plotBorderWidth: null,
plotShadow: false,
type: 'pie'
},
title: {
text: 'Population percentage city wise'
},
tooltip: {
pointFormat: '{series.name}: <b>{point.percentage:.1f}%</b>'
},
plotOptions: {
pie: {
allowPointSelect: true,
cursor: 'pointer',
dataLabels: {
enabled: true,
format: '<b>{point.name}</b>: {point.percentage:.1f} %',
style: {
color: (Highcharts.theme && Highcharts.theme.contrastTextColor) || 'black'
}
}
}
},
series: [{
name: "Brands",
colorByPoint: true,
data: seriesData
}]
});
}
$("#btnCreatePieChart").on('click', function (e) {
var pData = [];
pData[0] = $("#ddlyear").val();
var jsonData = JSON.stringify({ pData: pData });
$.ajax({
type: "POST",
url: "WebService1.asmx/getCityPopulation",
data: jsonData,
contentType: "application/json; charset=utf-8",
dataType: "json",
success: OnSuccess_,
error: OnErrorCall_
});
function OnSuccess_(response) {
var aData = response.d;
var arr = []
$.map(aData, function (item, index) {
var i = [item.city_name, item.population];
var obj = {};
obj.name = item.city_name;
obj.y = item.population;
arr.push(obj);
});
var myJsonString = JSON.stringify(arr);
var jsonArray = JSON.parse(JSON.stringify(arr));
drawPieChart(jsonArray);
}
function OnErrorCall_(response) {
alert("Whoops something went wrong!");
}
e.preventDefault();
});
//*
</script>
before that script write this code:
<script src="Scripts/jquery-2.2.3.min.js"></script>
<script src="Scripts/Highcharts-4.0.1/js/highcharts.js"></script>
and write this html code:
<select id="ddlyear">
<option>2010</option>
<option>2011</option>
<option>2012</option>
<option>2013</option>
<option>2014</option>
<option>2015</option>
</select>
<button id="btnCreatePieChart">Show </button>
<br />
<div>
<div id="container" style="width: 500px; height: 500px"></div>
</div>
but when i run project and fire the button,can not see anything,and chart not show to me,what happen?is my code incorrect?how can i solve that problem?thanks.
i think ajax can not call the web service!