Make Graphic Persistent In VB And GDI+?

I have a converted VB6 App that would draw irregular shapes on a PictureBox when I click on a button, and these irregular shapes would persist until I either close the App or erased the PictureBox to start the display anew.I converted my App to VB.Net to do the same, i.e. draw on a PictureBox again, but the drawn lines appear briefly and then, at the end of the drawing process, when my App returns control to the Operating System in wait for another event, the graphics disappear as if erased by the App (which I don't do of course).I have created a Graphics Object associated to my Picture Box as:

Dim CurrGraphics as System.Drawing.Graphics
CurrGraphics = PictureOut.CreateGraphics

I then use the DrawPolygon and DrawLine methods to add the irregular shapes I want:

CurrGraphics.DrawPolygon(CurrPen, Pts)
CurrGraphics.DrawLine(CurrPen, Pts(I).X, Pts(I).Y, Pts(I+1).X, Pts(I+1).Y)

where CurrPen is a defined Pen, and Pts is the Points() array with the coordinates of the displayed shape. Several dozens irregular shapes are drawn and then the subroutine stops, and returns to waiting for another request from the user.What could be the prime reason why graphics do not persist in a PictureBox, and are erased immediately after they are created ?

PS: I do not use the PainEvent of the PictureBox PictureOut, as in the example given in the VB documentation (below), as the display process is initiated by clicking on a button, and I cannot relate how to transfer control to the PaintEvent as below:

Private Sub Form1_Paint(sender As Object, pe As PaintEventArgs) Handles _
MyBase.Paint
' Declares the Graphics object and sets it to the Graphics object

[code]....