vb.net chart 动态曲线

'新建项目时，在默认窗体Form1上添加一个按钮，一个chart
Public Class Form1
    Dim x(10) As String, y(10) As Double '示例中显示11条数据
    Dim yy() As Double

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        '按钮单击事件模拟取数
        yy = GetValue()
        Dim i As Integer
        For i = 0 To yy.Length - 1
            y(i) = yy(i)
        Next

        Chart1.Series(0).ChartType = DataVisualization.Charting.SeriesChartType.Line
        Chart1.Series(0).Points.DataBindXY(x, y)

        Chart1.Series(0).IsValueShownAsLabel = True
        Chart1.Series(0).LabelForeColor = Color.Red
        Chart1.ChartAreas(0).AxisX.Minimum = 0
        Chart1.ChartAreas(0).AxisX.Maximum = yy.Length
        Chart1.ChartAreas(0).AxisX.Interval = 1
    End Sub
    Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load
        Chart1.Dock = DockStyle.Fill
        Button1.BringToFront()
        Chart1.ChartAreas(0).AxisX.MajorGrid.Enabled = False
        Chart1.ChartAreas(0).AxisY.MajorGrid.Enabled = False
    End Sub
    Function GetValue() As Array '这是一个模拟取数的函数
        Dim a As Integer = 0
        If yy Is Nothing Then
            a = 0
        Else
            a = yy.Length
        End If
        If a = 11 Then
            For i As Integer = 0 To 9
                yy(i) = yy(i + 1)
                x(i) = x(i + 1)
            Next
            yy(10) = Math.Round(a * Rnd(100) * 1.0264, 2)
            x(10) = Format(Now, "hh:mm:ss")
        Else
            ReDim Preserve yy(a)
            yy(a) = Math.Round(a * Rnd(100) * 1.0264, 2)
            x(a) = Format(Now, "hh:mm:ss")
        End If
        Return yy
    End Function
End Class