V W X Y Z v w x y z : only these letters are not being selected correctly using Select Case function in VBA.

This is the cleanest and closest to your original logic:

Select Case Asc(Mid(strSource, i, 1))
    Case 48 To 57, 65 To 90, 97 To 122   '0–9, A–Z, a–z
        strResult = strResult & Mid(strSource, i, 1)
End Select

This works perfectly for all letters including V–Z and v–z.

Hi Philipp Borer

Thank you for reaching out to Microsoft Q&A Forum and sharing your experience.

I reviewed your snippet and also reproduced this locally. Your uppercase ASCII range is 87 To 90, which matches W–Z only. V is ASCII 86, so it will never match that range. Changing it to 86 To 90 would include V. Also, your Select Case expression is a String (Mid(...)), but the statement mixes string cases ("a", "B", ...) with numeric ranges (118 To 122, 87 To 90). Numeric ranges only behave predictably when the Select Case expression is numeric.

To make the comparison consistent and avoid edge-case matching issues, converting the character to its Unicode value and comparing numeric ranges is the most reliable approach. I tested the following pattern and it correctly keeps all letters including V–Z and v–z, plus digits:

Function AlphaNumericOnly_FIXED(ByVal strSource As String) As String
    Dim i As Long
    Dim ch As String
    Dim code As Long
    Dim strResult As String
    
    For i = 1 To Len(strSource)
        ch = Mid$(strSource, i, 1)
        code = AscW(ch)
        
        Select Case code
            Case 48 To 57, 65 To 90, 97 To 122   '0-9, A-Z, a-z
                strResult = strResult & ch
        End Select
    Next i
    
    AlphaNumericOnly_FIXED = strResult
End Function

Please let me know how things go on your side as your update can also assist others in the community who may be facing the same issue.

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It seems that characters and codes cannot be mixed.

To use codes:

Select Case AscW(Mid(strSource, i, 1))
  Case 48 To 57, _
       65 To 90, _
       97 To 122
    strResult = strResult & Mid(strSource, i, 1)
End Select

To use characters:

Select Case Mid(strSource, i, 1)
  Case "1" To "9", _
       "A" To "Z", _
       "a" To "z"
    strResult = strResult & Mid(strSource, i, 1)
End Select

Perhaps Regular Expressions or other methods can be used too.