Chartjs-Cannot create property 'datasets' on string

I have fixed my issue

Here is the new server code:

<WebMethod()>
Public Shared Function GetChart() As List(Of Object)

    Dim iData As New List(Of Integer)()
    Dim sColor As New List(Of String)()
    Dim sLabel As New List(Of String)()
    Dim chartData As New List(Of Object)()

    Dim objConn As New SqlConnection(ConfigurationManager.ConnectionStrings("conProcase").ToString)
    objConn.Open()

    Try

       '... my db stuff

        Do While objRdr.Read()
            iData.Add(Convert.ToInt32(objRdr("iCount")))
            sColor.Add([String].Format("#{0:X6}", New Random().Next(&H1000000)))
            sLabel.Add(objRdr("Co_Desc"))

        Loop

        objRdr.Close()


    Catch ex As Exception


    Finally

        If Not IsNothing(objConn) Then
            objConn.Close()
            objConn = Nothing
        End If

    End Try

    chartData.Add(iData)
    chartData.Add(sColor)
    chartData.Add(sLabel)

    Return chartData


End Function

The jquery side:

 function LoadChart() {

    var ctx = document.getElementById("chart-area").getContext('2d');


 $.ajax({
    type: "POST",
    url: "_TempEntrada.aspx/GetChart",
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: function (r) {
            var sData =
            {
                labels: r.d[2] ,
                datasets: [
                    {
                        backgroundColor: r.d[1],
                        data: r.d[0] 
                    },

                ]
            };

        var config = {
            type: 'doughnut',
            data:sData,
            options: {
                responsive: true,
                legend: {
                    position: 'top',
                },
                title: {
                    display: true,
                    text: 'Chart.js Doughnut Chart'
                },
                animation: {
                    animateScale: true,
                    animateRotate: true
                }
            }
        };

        var myDoughnutChart = new Chart(ctx, config);



    },
    failure: function (response) {
        alert('There was an error.');
    }
});
}