Converting Numbers to Excel Letter Column vb.net - vb.net

Question

I am trying to write data to excel files using vb.net. So I my function which converts number column into excel letter columns.
Public Function ConvertToLetter(ByRef iCol As Integer) As String
Dim Reminder_Part As Integer = iCol Mod 26
Dim Integer_Part As Integer = Int(iCol / 26)
If Integer_Part = 0 Then
ConvertToLetter = Chr(Reminder_Part + 64)
ElseIf Integer_Part > 0 And Reminder_Part <> 0 Then
ConvertToLetter = Chr(Integer_Part + 64) + Chr(Reminder_Part + 64)
ElseIf Integer_Part > 0 And Reminder_Part = 0 Then
ConvertToLetter = Chr(Integer_Part * 26 + 64)
End If
End Function
The Function works ok with any other numbers.
For example,
1 => A
2 => B
...
26 => Z
27 => AA
...
51 => AY
52 => t (And here is when it start to went wrong) It is suppose to return AZ, but it returned t.
I couldn't figure out what part I made a mistake. Can someone help me or show me how to code a proper function of converting numbers to excel letter columns using vb.net.

Answer 1

This should do what you want.
Private Function GetExcelColumnName(columnNumber As Integer) As String
Dim dividend As Integer = columnNumber
Dim columnName As String = String.Empty
Dim modulo As Integer
While dividend > 0
modulo = (dividend - 1) Mod 26
columnName = Convert.ToChar(65 + modulo).ToString() & columnName
dividend = CInt((dividend - modulo) / 26)
End While
Return columnName
End Function

Answer 2

This will work up to 52.
Public Function ConvertToLetterA(ByRef iCol As Integer) As String
Select Case iCol
Case 1 To 26
Return Chr(iCol + 64)
Case 27 To 52
Return "A" & Chr(iCol - 26 + 64)
End Select
End Function
On a side note, you can write XLSX files directly with EPPlus via .Net. You can use letter notation for columns if you wish, or you can use numbers.

Answer 3

There are a couple flaws in the logic, the second else clause is not required and the operations should be zero based.
Public Function ConvertToLetter(ByRef iCol As Integer) As String
Dim col As Integer = iCol - 1
Dim Reminder_Part As Integer = col Mod 26
Dim Integer_Part As Integer = Int(col / 26)
If Integer_Part = 0 Then
ConvertToLetter = Chr(Reminder_Part + 65)
Else
ConvertToLetter = Chr(Integer_Part + 64) + Chr(Reminder_Part + 65)
End If
End Function