Working with Perso-Arabic Text (count + joining issues)

Question

I'm trying to display the Persian alphabet in the Debug window in order. Once it reaches the final letter, subsequent letters will be multiplied by the group they are in. So, for example, if I want to display alef (ا) - Persian for the letter "A", I would start with the index of 1. If I reach an index of 33 (Persian has 32 letters), it should display (اا).

The code below works just fine for the Latin alphabet (e.g. "abcdefj..."), but with Persian/Arabic, I've got two problems.

1. It gives a count of 33 instead of 32 - i.e. after the letter "ه" it produces a blank character. I suspect it is this, but don't know how to account for it.

2. For characters that need to double up, like "ش ش" (without the space) it shows as "شش".

   Sub Main()
       Dim t As New PersianAlphabet
       For i = 1 To 50
           Debug.WriteLine(t.NextLetter())
       Next
   End Sub
   
   Public Class PersianAlphabet
       Private charArray As String
       Private charCount As Integer
       Private CurrentNumber As Integer = 0
       Sub New()
           'Dim charArray1() = {"ا", "ب", "پ", "ت", "ث", "ج", "چ", "ح", "خ", "د", "ذ", "ر", "ز", "ژ", "س", "ش", "ص", "ض", "ط", "ظ", "ع", "غ", "ف", "ق", "ک", "گ", "ل", "م", "ن", "و", "ه‍", "ی"}
           'Dim joined As String = String.Join("", charArray1)
           'Me.charArray = joined
           Me.charArray = "ابپتثجچحخدذرزژسشصضطظعغفقکگلمنوه‍ی"
           Me.charCount = charArray.ToCharArray.Count
       End Sub
       Public Function NextLetter(Optional ByVal StartAt As Integer = 1) As String
           Dim count = (Me.CurrentNumber + StartAt)
   
           Dim divisor = count / Me.charCount
           Dim outstring As New StringBuilder
   
           If divisor <= 1 Then
               outstring.Append(charArray(Int32.Parse(count - 1)))
           Else
               Dim tempAlphaCount = Int(divisor) + 1
               Dim groupRange = Int(divisor) * Me.charCount
               Dim alphaIndex = count - groupRange
               If alphaIndex = 0 Then
                   tempAlphaCount = tempAlphaCount - 1
                   alphaIndex = Me.charCount
               End If
               alphaIndex -= 1
   
               For i = 0 To tempAlphaCount - 1
                   outstring.Append(charArray(Int32.Parse(alphaIndex)))
               Next
           End If
   
           Me.CurrentNumber += 1
           Return outstring.ToString
       End Function
   End Class
   

Has anyone dealt with these two kinds of issues before? Any thoughts/advice?

Answer 1

Figured out that there is a Unicode of 2805 (not 2804 as expected) within the string. Removing that gives the correct count. Putting that between two letters also allows for non-joining letters.