Add data table with legend keys to ASP.Net Chart using C# and VB.Net

Check with below code.

Private Sub chart1_PrePaint(ByVal sender As Object, ByVal e As ChartPaintEventArgs)
    Dim cell As LegendCell = TryCast(e.ChartElement, LegendCell)
    If cell IsNot Nothing AndAlso cell.Tag Is Nothing Then
        Dim r As RectangleF = e.ChartGraphics.GetAbsoluteRectangle(e.Position.ToRectangleF())
        e.ChartGraphics.Graphics.DrawRectangle(Pens.DimGray, Rectangle.Round(r))
        If cell.CellSpan <> 1 Then e.ChartGraphics.Graphics.DrawLine(Pens.White, r.Left, r.Top + 1, r.Left, r.Bottom - 1)
    End If
End Sub

Private Sub Page_Load(ByVal sender As Object, ByVal e As ChartPaintEventArgs) Handles Me.Load
    chart1.Legends(0).Enabled = False
    chart1.Legends.Add(New Legend("customLegend"))
    Dim L As Legend = chart1.Legends(1)
    L.DockedToChartArea = chart1.ChartAreas(0).Name
    L.Docking = Docking.Bottom
    L.IsDockedInsideChartArea = False
    L.Alignment = StringAlignment.Center
    addValuesToLegend(L, chart1.Series(0), False)

    For Each s As Series In chart1.Series
        addValuesToLegend(L, s, True)
    Next
End Sub

Private Sub addValuesToLegend(ByVal L As Legend, ByVal S As Series, ByVal addYValues As Boolean)
    Dim newItem As LegendItem = New LegendItem()
    newItem.MarkerStyle = S.MarkerStyle
    newItem.MarkerColor = S.Color
    If S.MarkerStyle = MarkerStyle.None Then
        newItem.ImageStyle = LegendImageStyle.Rectangle
        newItem.BorderColor = Color.Transparent
        newItem.Color = S.Color
    Else
        newItem.ImageStyle = LegendImageStyle.Marker
    End If

    newItem.Cells.Add(LegendCellType.SeriesSymbol, "", ContentAlignment.MiddleCenter)
    newItem.Cells.Add(LegendCellType.Text, If(addYValues, S.Name, ""), ContentAlignment.MiddleLeft)
    newItem.Cells(1).CellSpan = 2

    If Not addYValues Then
        newItem.ImageStyle = LegendImageStyle.Line
        newItem.Color = Color.Transparent
        newItem.Cells(0).Tag = "*"
    End If

    For Each dp As DataPoint In S.Points
        Dim t As String = dp.YValues(0).ToString(S.Tag.ToString())
        If Not addYValues Then t = DateTime.FromOADate(dp.XValue).ToString("M\/d\/yyyy")
        newItem.Cells.Add(LegendCellType.Text, t, ContentAlignment.MiddleCenter)
    Next

    For Each cell In newItem.Cells
        cell.Margins = New Margins(25, 20, 25, 20)
    Next

    L.CustomItems.Add(newItem)
End Sub