Generate a Random String Key in VB.NET

Option Strict On
Imports System.Text
''' <date>27072005</date><time>070339</time>
''' <type>class</type>
''' <summary>
''' REQUIRES PROPERTIES: KeyLetters, KeyNumbers, MaxChars
''' </summary>
Public Class RandomKeyGenerator
    Dim Key_Letters As String
    Dim Key_Numbers As String
    Dim Key_Chars As Integer
    Dim LettersArray As Char()
    Dim NumbersArray As Char()

    ''' <date>27072005</date><time>071924</time>
    ''' <type>property</type>
    ''' <summary>
    ''' WRITE ONLY PROPERTY. HAS TO BE SET BEFORE CALLING GENERATE()
    ''' </summary>
    Protected Friend WriteOnly Property KeyLetters() As String
        Set(ByVal Value As String)
            Key_Letters = Value
        End Set
    End Property
    ''' <date>27072005</date><time>071924</time>
    ''' <type>property</type>
    ''' <summary>
    ''' WRITE ONLY PROPERTY. HAS TO BE SET BEFORE CALLING GENERATE()
    ''' </summary>
    Protected Friend WriteOnly Property KeyNumbers() As String
        Set(ByVal Value As String)
            Key_Numbers = Value
        End Set
    End Property
    ''' <date>27072005</date><time>071924</time>
    ''' <type>property</type>
    ''' <summary>
    ''' WRITE ONLY PROPERTY. HAS TO BE SET BEFORE CALLING GENERATE()
    ''' </summary>
    Protected Friend WriteOnly Property KeyChars() As Integer
        Set(ByVal Value As Integer)
            Key_Chars = Value
        End Set
    End Property

    ''' <date>27072005</date><time>072344</time>
    ''' <type>function</type>
    ''' <summary>
    ''' GENERATES A RANDOM STRING OF LETTERS AND NUMBERS. LETTERS CAN BE RANDOMLY CAPITAL OR SMALL.
    ''' </summary>
    ''' <returns type="String">RETURNS THE RANDOMLY GENERATED KEY</returns>
    Function Generate() As String
        Dim i_key As Integer
        Dim Random1 As Single
        Dim arrIndex As Int16
        Dim sb As New StringBuilder
        Dim RandomLetter As String

        ''' CONVERT LettersArray & NumbersArray TO CHARACTR ARRAYS
        LettersArray = Key_Letters.ToCharArray
        NumbersArray = Key_Numbers.ToCharArray

        For i_key = 1 To Key_Chars
            ''' START THE CLOCK    - LAITH - 27/07/2005 18:01:18 -
            Randomize()
            Random1 = Rnd()
            arrIndex = -1
            ''' IF THE VALUE IS AN EVEN NUMBER WE GENERATE A LETTER, OTHERWISE WE GENERATE A NUMBER   - LAITH - 27/07/2005 18:02:55 -
            ''' THE NUMBER '111' WAS RANDOMLY CHOSEN. ANY NUMBER WILL DO, WE JUST NEED TO BRING THE VALUE ABOVE '0'     - LAITH - 27/07/2005 18:40:48 -
            If (CType(Random1 * 111, Integer)) Mod 2 = 0 Then
                ''' GENERATE A RANDOM LOCATION  IN THE LETTERS CHARACTER ARRAY   - LAITH - 27/07/2005 18:47:44 -
                Do While arrIndex < 0
                    arrIndex = Convert.ToInt16(LettersArray.GetUpperBound(0) * Random1)
                Loop
                RandomLetter = LettersArray(arrIndex)
                ''' CREATE ANOTHER RANDOM NUMBER. IF IT IS ODD, WE CAPITALIZE THE LETTER    - LAITH - 27/07/2005 18:55:59 -
                If (CType(arrIndex * Random1 * 99, Integer)) Mod 2 <> 0 Then
                    RandomLetter = LettersArray(arrIndex).ToString
                    RandomLetter = RandomLetter.ToUpper
                End If
                sb.Append(RandomLetter)
            Else
                ''' GENERATE A RANDOM LOCATION  IN THE NUMBERS CHARACTER ARRAY   - LAITH - 27/07/2005 18:47:44 -
                Do While arrIndex < 0
                    arrIndex = Convert.ToInt16(NumbersArray.GetUpperBound(0) * Random1)
                Loop
                sb.Append(NumbersArray(arrIndex))
            End If
        Next
        Return sb.ToString
    End Function
End Class