Drawing a line into a picture box

Question

Hello every body
I 'm new in vb.net  I tried to write a little app drawing a line into a picture box and
show it
here the code
Public Class Form1
Private Sub draws()
Dim mypen As Pen
Dim gr As System.Drawing.Graphics
gr = panel2.CreateGraphics
mypen = New Pen(Color.Chocolate, 3)
gr.DrawLine(mypen, 20, 20, 700, 700)
End Sub

Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
DisplayPanel()
End Sub
Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
draws()
End Sub

Private Sub DisplayPanel()
Me.Panel2.BackgroundImage = Image.FromFile("E:\drawnet\Draw\Draw\bin\Debug\lcws\board.bmp")
Me.Panel2.Width = Me.Panel2.BackgroundImage.Width
Me.Panel2.Height = Me.Panel2.BackgroundImage.Height
Me.Panel2.Left = Me.Width / 2 - Me.Panel2.Width / 2
Me.Panel2.Top = Me.Height / 2 - Me.Panel2.Height / 2
End Sub

End Class
panel2 is the name of  the picture box.
When i run the app i didn't see the line  but only if i create an event like mouse click etc. why?
thanks for explanation