Highchart piechart无法从数据库中获取数据c＃

Question

<script type="text/javascript">
    function drawPieChart(seriesData) {

        $('#container').highcharts({
            chart: {
                plotBackgroundColor: null,
                plotBorderWidth: null,
                plotShadow: false,
                type: 'pie'
            },
            title: {
                text: 'Blood Volume'
            },
            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] = $('<%=ddlLocation.ClientID%>').val();

        var jsonData = JSON.stringify({ pData: pData });

        $.ajax({
            type: "POST",
            url: "WebForm1.aspx/getBloodInventory",
            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.id, item.volume];
                var obj = {};
                obj.name = item.id;
                obj.y = item.volume;
                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>

[的WebMethod]

    public List<bloodInventory> getBloodInventory(List<string> pData)
    {
        List<bloodInventory> p = new List<bloodInventory>();


        string conn = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;


        using (SqlConnection cn = new SqlConnection(conn))
        {
            string myQuery = "select blood_group_id,SUM(volume) as volume from BloodInventory b, Donors d where (b.donor_id = d.donor_id and blood_bank_id=@blood_bank_id)";
            SqlCommand cmd = new SqlCommand();
            cmd.CommandText = myQuery;
            cmd.CommandType = CommandType.Text;
            cmd.Parameters.AddWithValue("@blood_bank_id", pData[0]);
            cmd.Connection = cn;
            cn.Open();
            SqlDataReader dr = cmd.ExecuteReader();
            if (dr.HasRows)
            {
                while (dr.Read())
                {
                    bloodInventory cpData = new bloodInventory();
                    cpData.id = dr["blood_group_id"].ToString();
                    cpData.volume = Convert.ToInt32(dr["volume"].ToString());
                    p.Add(cpData);
                }
            }
        }
        return p;
    }

以上是我的代码，我想根据下拉列表中的选择显示一个饼图。当我点击按钮显示它显示错误404的网址没有找到，我可以知道是什么问题？