(About GDI+) How to clear the image printed by Graphics.DrawImage()

How can I clear the image which is printed by the "Graphics.DrawImage()" on the form.
Dim gra As Graphics
gra = Me.CreateGraphics()
Dim path As String
path = "e:\test2.bmp"
Dim picture As Image
picture = New Bitmap(path)
gra.DrawImage(picture, 0, 0)

I just want to erase the picture(test2.bmp) on the form.
And I dooooooon't want to use me.refresh(), because it's in a very low efficiency.

please give me the right code! Thanks very much!

Try Me.Invalidate and tell me its efficacy in comparison to Me.Refresh

the efficency is quite the same
thank you anyway

me.refresh seems pretty efficient on my system (1.4 GHz p4). I can easily refresh the form about 30 times a second while using .NET's built-in double buffering (the double buffering completely stops the flickering). I can refresh the form a lot faster if I disable the double buffering, but then it flickers way too much.