I'm trying to display some data in Google Charts but get this error:

Data column(s) for axis #0 cannot be of type string..

I have two properties from this class:

public class GAStatistics

{

    public string Date { get; set; }

    public string Visitors { get; set; }

}

I'm passing this a list of these properties from this controller:

public class GAStatisticsController : Controller

{

    

     //GET: /ShopStatistics/





    public ActionResult GetData()

    {

        return Json(CreateCompaniesList(), JsonRequestBehavior.AllowGet);

    }





    private IEnumerable<GAStatistics> CreateCompaniesList()

    {

        

        List<GAStatistics> ListGaVisitors = new List<GAStatistics>();



        foreach (var row in d.Rows)

        {



            GAStatistics GaVisits = new GAStatistics(row[0], row[1]);

            ListGaVisitors.Add(GaVisits);

        }

        



        return ListGaVisitors;

   

    }



}

To this view of which I pass the list from the controller:

<script type="text/javascript" src="https://www.google.com/jsapi"></script>

    

    <script type="text/javascript">

    

        google.load("visualization", "1", { packages: ["corechart"] });

        google.load("visualization", "1", { packages: ["treemap"] });

        google.setOnLoadCallback(drawChart);

        function drawChart() {

            $.get('/GAStatistics/GetData', {},

                function (data) {

                    var tdata = new google.visualization.DataTable();

    

                    tdata.addColumn('string', 'Date');

                    tdata.addColumn('string', 'Visitors');

            

    

                    for (var i = 0; i < data.length; i++) {

                        //tdata.addRow([data[i].Year, data[i].Salary, data[i].Expense]);

                        tdata.addRow([data[i].Date, data[i].Visitors]);

                    }

    

    

    

                    var options = {

                        title: "Expenses, salary For the current year"

                    };

    

                    var chart1 = new google.visualization.AreaChart(document.getElementById('chart_div1'));

    

                    chart1.draw(tdata, options);



                });

    

    

        }

    </script>

Any idea?