How to clear Data(Points, Series) in MSchart?

con.Open()
        '********************************************************************
        Dim startDate As DateTime = DirectCast(dtpStart.Value, DateTime)
        Dim endDate As DateTime = DirectCast(dtpEnd.Value, DateTime)
        Dim ts As TimeSpan = endDate.Subtract(startDate)

        Dim days As Integer = ts.Days

        Try


            Dim str As String = "select distinct empfullname from employee where department='Transcription' and designation='" + cmbDesig.Text + "' order by designation, empfullname "
            Dim ds As DataSet

            ds = cnn.ExecuteDataset(str)


            Dim ds2 As New DataSet
            For i As Integer = 0 To ds.Tables(0).Rows.Count - 1

                Dim cn As Integer = 0
                cmd.CommandText = "select sum(actuallinecount), designation from linecountdetails where (dateoflinecount between '" + Format(Convert.ToDateTime(dtpStart.Value), "yyyy-MM-dd") + "' and '" + Format(Convert.ToDateTime(dtpEnd.Value), "yyyy-MM-dd") + "') and empfullname='" + ds.Tables(0).Rows(i).ItemArray(0).ToString() + "' "
                cmd.Connection = con
                dr = cmd.ExecuteReader()
                While dr.Read()
                    If dr(0) Is DBNull.Value Then
                        cn = 0
                    Else
                        cn = dr(0)
                    End If

                End While
                dr.Close()

                Dim lc As Double = cn
                Chart1.Series("Series1").Points.Add(lc).AxisLabel = ds.Tables(0).Rows(i).ItemArray(0).ToString()

                Chart1.ChartAreas("ChartArea1").AxisY.Title = "Line Count"
                Chart1.ChartAreas("ChartArea1").AxisX.Title = "Employee"

                Chart1.ChartAreas("ChartArea1").AxisX.Interval = 1
                Chart1.ChartAreas("ChartArea1").AxisX.IntervalOffset = 1

                Chart1.Series("Series1").Points(i).ToolTip() = lc
            Next
            'End If

            Chart1.DataSource = ds.Tables("linecountdetails")
            Chart1.DataBind()

            con.Close()

        Catch ex As Exception

        End Try