Public Class Form1
    Dim bmp As New Bitmap(400, 400)
    Dim g As Graphics = Graphics.FromImage(bmp)
       Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
         System.EventArgs) Handles Button1.Click
        Dim rnd As New Random
        g.DrawLine(New Pen(Color.Yellow), 0, 0, rnd.Next(400), rnd.Next(400))
        PictureBox1.Image = bmp
    End Sub
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        PictureBox1.BackColor = Color.Black
    End Sub
    Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        g.Dispose()
        bmp.Dispose()
    End Sub
End Class