Public Class Form1
 
    Private Sub Form1_Click(ByVal sender As Object, ByVal e As _
      System.EventArgs) Handles Me.Click
        Invalidate()
    End Sub
 
    Private Sub Form1_MouseMove(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles Me.MouseMove
 
        Dim g As Graphics = CreateGraphics()
        Dim p As Pen = New Pen(BackColor, 0)
 
        g.Clear(BackColor)
 
        Dim ptMitte As New PointF(CSng(ClientSize.Width / 2), CSng( _
          ClientSize.Height / 2))
 
        Static ptmaus As New PointF
 
        Dim br As New SolidBrush(Color.Black)
        Dim fn As New Font("Arial", 10)
 
        ' Löschen
        'g.DrawLine(p, ptMitte, ptmaus)
 
        ' Lote
        g.DrawLine(p, ptmaus, New PointF(ptmaus.X, ptMitte.Y))
        g.DrawLine(p, ptMitte, New PointF(ptmaus.X, ptMitte.Y))
 
        ' Sichtbar zeichnen
        ptmaus.X = CSng(e.X)
        ptmaus.Y = CSng(e.Y)
        p.Color = Color.Black
        g.DrawLine(p, ptMitte, ptmaus)
 
        ' Lote
        p.Color = Color.Black
        g.DrawLine(p, ptmaus, New PointF(ptmaus.X, ptMitte.Y))
        g.DrawLine(p, ptMitte, New PointF(ptmaus.X, ptMitte.Y))
 
        'g.DrawString("a", fn, br, 0, 10)
        'g.DrawString("b", fn, br, 0, 40)
        'g.DrawString("c", fn, br, 0, 50)
 
 
    End Sub
 
End Class