Public Class Parabola
    ' margin around picture in pixels
    Const MARGINSIZE As Integer = 10
    ' grid size for strings in pixels
    Const STEPSIZE As Integer = 10
    ' paint handler
    Private Sub Parabola_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles MyBase.Paint
        ' get size of client area
        Dim client As Size = ClientSize
        ' calculate co-ordinates of plot
        Dim xl As Integer = MARGINSIZE
        Dim xr As Integer = client.Width - MARGINSIZE
        Dim yt As Integer = MARGINSIZE
        Dim yb As Integer = client.Height - MARGINSIZE
        ' calculate how many steps fit down the screen 
        Dim size = STEPSIZE * ((yb - yt) \ STEPSIZE)
        ' draw the lines
        For i As Integer = 0 To size Step STEPSIZE
            e.Graphics.DrawLine(Pens.Blue, xl, yb - i, xl + size - i, yb)
        Next
    End Sub
    ' handle form size changed event
    Private Sub Parabola_Resize(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Resize
        Refresh()
    End Sub
End Class