VBnet ZedGraph可以用buttom的单击触发绘图事件吗？

如图所示的一个Form，根据Case：

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim junk As ZedGraph.ZedGraphControl
        junk = ZedGraphControl2
        junk.GraphPane.Title = "Test Case for VB"
        junk.IsShowPointValues = False

        Dim x(100) As Double
        Dim y(100) As Double
        Dim i As Integer
        Randomize()
        For i = 1 To 100
            x(i) = i / 100 * 6.3
            y(i) = Math.Sin(x(i))
        Next

        junk.GraphPane.AddCurve("Sine Wave", x, y, Color.Blue, ZedGraph.SymbolType.XCross)
        junk.GraphPane.AxisFill = New ZedGraph.Fill(Color.White, Color.LightGoldenrodYellow)
        junk.AxisChange()
    End Sub

直接运行可以显示绘图，那么将该段代码置入Show的Buttom中，以Click为触发事件就无法绘图，请问各位如何解决？