如何在双缓冲控件上使用GDI绘图

[r040bk20032030]

我想在一个自定义控件上画图，显示当前时间。代码如下
Public Class GDIPanel
Inherits Panel
Dim bmp As Image
Public Property image() As Image
Get
Return bmp
End Get
Set(ByVal value As Image)
bmp = value
End Set
End Property

Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
If Not Me.image Is Nothing Then
e.Graphics.DrawImage(Me.image, 0, 0, Me.Width, Me.Height)
End If
OnDraw()
End Sub

Public Sub OnDraw()
Dim g As Graphics
g = Me.CreateGraphics
Dim t As String
t = CStr(Now.Hour) + ":" + CStr(Now.Minute) + ":" + CStr(Now.Second)
Dim font As Font = New Font("Microsoft Sans Serif", 40, FontStyle.Regular)
g.DrawString(t, font, Brushes.Lime, 0, 0)
End Sub

Public Sub New()
' DoubleBuffered = True
End Sub
End Class
可是，每次把双缓冲开启，DoubleBuffered= True 时，便无法显示时间。是不是那个缓存的图层遮盖掉了当前图层啊？这个问题该如何解决啊？

[r040bk20032030]

经常在网上看见人家说，把DoubleBuffered设为True。然后在内存中画图。画完后导入到屏幕上。那究竟是怎么回事啊。
我是菜鸟，看不太懂。目前只会利用诸如 Dim g As Graphics g = Me.CreateGraphics 来绘图。
哪位大哥能给我解释一下吗？

[r040bk20032030]

有或者是给我一个 在PictureBox控件上 画当前时间的代码

[yilanwuyu123]

设置双缓冲好像还要设置UserPaint属性

[r040bk20032030]

这个怎么设啊？
能不能给我一个在双缓冲控件（如PictureBox）上画图的例子啊？