Compare with InStr Check if Array Item is in a String

I have an Array of the Alphabet

I have a dataset that I page through and add the first letter of each category to a string


called sActiveLetters Itry to write links out as Anchors but when I run code it is not returning true.

sActiveLetters is full eg.  abcdefghijklmnoprstvw

My Code is Below

          Dim sRetStr As String = ""
          Dim sCurrentLetter As String = ""
          Dim sLastLetter As String = ""
          Dim sActiveFirstLetters As String = ""
          Dim vAlphabet(26) As String
          vAlphabet(1) = "A"
          vAlphabet(2) = "B"
          vAlphabet(3) = "C"
          vAlphabet(4) = "D"
                   etc....


          For Each dr In CatlistDS.Tables("Cats").Rows
              sCurrentLetter = LCase(Left(Convert.ToString(dr.Item("tbo_Category")), 1))
              If sCurrentLetter <> sLastLetter Then
                  sActiveFirstLetters = sActiveFirstLetters & sCurrentLetter
                  sRetStr = sRetStr & "<a name=""" & sCurrentLetter & """></a>"
                  sRetStr = sRetStr & "<h2>" & sCurrentLetter & "</h2><hr>"
              End If
              sRetStr = sRetStr & "<a class=CatsList >" & Convert.ToString(dr.Item("tbo_Category")) & "</a><BR>"
              sLastLetter = LCase(Left(Convert.ToString(dr.Item("tbo_Category")), 1))
        
          Next

'' now, you've got the categories in a variable called "sRetStr" -- let's write out the alphabet letter list for page anchors:
          For i = 1 To 26
              If InStr(sActiveFirstLetters, vAlphabet(i)) > 0 Then
                  ' then it's valid, write a link!
                  Response.Write("<a class=Listing href=""#" & vAlphabet(i) & """>" & vAlphabet(i) & "</a>&nbsp;&nbsp;")
                  '  Else
                  '' didn't find the letter in my string of active letters, so I guess it's not active...
                  '  Response.Write("<span class=inactiveListing>" & vAlphabet(i) & "</a>&nbsp;")
              End If
          Next

It is the 3 lines below that are not executing as planned

If InStr(sActiveFirstLetters, vAlphabet(i)) > 0 Then
                  ' then it's valid, write a link!
                  Response.Write("<a class=Listing href=""#" & vAlphabet(i) & """>" & vAlphabet(i) & "</a>&nbsp;&nbsp;")

Any help would be most appreciated, it is driving me nuts