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)
 
 
        LinieMitText(g, "a", ptMitte, ptmaus)
        LinieMitText(g, "b", ptmaus, New PointF(ptmaus.X, ptMitte.Y))
        LinieMitText(g, "c", ptMitte, New PointF(ptmaus.X, ptMitte.Y))
 
    End Sub
 
 
 
 
 
 
 
    ''' <summary>
    ''' Text steht direkt auf der Linienmitte, zentriert auf beiden Achsen, 
    ' nicht gedreht um Liniensteigung
    ''' </summary>
    ''' <param name="pGR"></param>
    ''' <param name="pP1"></param>
    ''' <param name="pP2"></param>
    ''' <remarks></remarks>
    Private Sub LinieMitText(ByVal pGR As Graphics, ByVal pText As String, _
      ByVal pP1 As PointF, ByVal pP2 As PointF)
 
        Dim l_TextAnsatzStelle As New Point
        Dim l_SF As New StringFormat
 
        If pP1.X < pP2.X Then
            l_TextAnsatzStelle.X = pP1.X + 0.5 * (pP2.X - pP1.X)
        Else
            l_TextAnsatzStelle.X = pP2.X + 0.5 * (pP1.X - pP2.X)
        End If
 
        If pP1.Y < pP2.Y Then
            l_TextAnsatzStelle.Y = pP1.Y + 0.5 * (pP2.Y - pP1.Y)
        Else
            l_TextAnsatzStelle.Y = pP2.Y + 0.5 * (pP1.Y - pP2.Y)
        End If
 
        l_SF.LineAlignment = StringAlignment.Center
        l_SF.Alignment = StringAlignment.Center
 
        pGR.DrawLine(Pens.Black, pP1, pP2)
        pGR.DrawString(pText, New Font("Arial", 12), Brushes.Blue, _
          l_TextAnsatzStelle, l_SF)
 
    End Sub
 
 
End Class