"Table has no columns "- by asp.net for Google chart// Please Help and Thanks! -candy

[candy]

Hello, 

I get the   "Table has no columns " on get json by asp.net for Google chart.

Could you help me here please ...?  Thank you all! I am stuck here. 

Method (1) I test the  Url  for directly to Json on my iis  EX:   http://localhost/candy_json_D3/sampleData.json   => fail 

Method (2) I use the  Url  asp.net   public string GetChartData()  =>"Table has no columns "

        

          {    return JsonString;

        }

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I. sampleData.json

{

  "cols": [

        {"id":"","label":"Topping","pattern":"","type":"string"},

        {"id":"","label":"Slices","pattern":"","type":"number"}

      ],

  "rows": [

        {"c":[{"v":"Mushrooms","f":null},{"v":3,"f":null}]},

        {"c":[{"v":"Onions","f":null},{"v":1,"f":null}]},

        {"c":[{"v":"Olives","f":null},{"v":1,"f":null}]},

        {"c":[{"v":"Zucchini","f":null},{"v":1,"f":null}]},

        {"c":[{"v":"Pepperoni","f":null},{"v":2,"f":null}]}

      ]

}

------------------------------------------------------------------------------------------------------------------------------------

II. <script type="text/javascript">

        // Load the Visualization API and the piechart package.

        google.charts.load('current', { 'packages': ['corechart'] });

        // Set a callback to run when the Google Visualization API is loaded.

        google.charts.setOnLoadCallback(drawChart);

        function drawChart() {

            var jsonData = $.ajax({

                url: "ColumnChart.aspx/GetChartData",     // how could I read it it get the right type here ?

                dataType: "json",

                data: '{}',

                success: function (response) {

                    drawchart(response.d); // calling method  

                },

                error: function () {

                    alert("Error loading data! Please try again.");

                }

                //async: false

            }).responseText;

            // Create our data table out of JSON data loaded from server.

            var data = new google.visualization.DataTable(jsonData);

            // Instantiate and draw our chart, passing in some options.

            var chart = new google.visualization.PieChart(document.getElementById('chart_div'));

            chart.draw(data, { width: 400, height: 240 });

        }

    </script>

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III. Asp.net 

 public string GetChartData()

        { 

           // Get data from "http://localhost/candy_json_D3/sampleData.json "

            return JsonString;

        }

BR

Candy