how to make a working kegen with c++ or visual basic 2010

TextBox1.Text = Int(Rnd() * 4)
Select Case TextBox1.Text
Case 0
TextBox1.Text = ""
Case 1
TextBox1.Text = "F4-GS-55-X7"
Case 2
TextBox1.Text = "DT-3Y-PL-SJ"
Case 3
TextBox1.Text = "57-KL-D7-AW"
Case 4
TextBox1.Text = "JX-MU-9S-S4"
Case 5
TextBox1.Text = "SZ-J5-B7-DT"
End Select

    Dim Append As String = Nothing, Out As String = Nothing
    If Letters Then Append &= "aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStTuUvVwWxXyYzZ"
    If Numbers Then Append &= "1234567890"
     Dim R As New System.Random, S As New System.Text.StringBuilder(Append)
    For I = 0 To Length - 1 : Out &= S.Chars(R.Next(0, S.Length)) : Next
    Return Out