Dim rnd As New Random(Now.Millisecond)
 
  Public Function CreateRandomString(theLen As Short, art As RandomTextType) As _
    String
        Const lowerChars As String = "abcdefghijklmnopqrstuvwxyzäöüß"
        Const upperChars As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZÄÖÜ"
        Const numericChars As String = "0123456789"
        Const specChars As String = "!§$%&/()=?{[]}+*~#'-_.:,;<>"
 
        Dim rs As String = ""
        Dim ast As String = "", le, ix As Integer
 
        ' Zusammensetzung gemäß vorgegebener Art
        Select Case art
            Case RandomTextType.LowerCaseLetters
                ast = lowerChars
            Case RandomTextType.UpperCaseLetters
                ast = upperChars
            Case RandomTextType.LowerCaseLettersMixedNumbers
                ast = lowerChars + numericChars
            Case RandomTextType.UpperCaseLettersMixedNumbers
                ast = upperChars + numericChars
            Case RandomTextType.MixedAll
                ast = lowerChars + upperChars + numericChars + specChars
        End Select
 
        le = ast.Length - 1
        For i As Short = 1 To theLen
            ix = rnd.Next(0, le + 1)
            rs &= ast.Substring(ix, 1)
        Next
 
        ' Rückgabe des Strings
        Return rs
  End Function