C# - Get Excel Column Name from Number

private static String GetExcelColumnLetters(Int32 column, Boolean indexIsZeroBased)
{
    if (indexIsZeroBased == false)
    {
        column--;
    }
    Int32 firstLetter = column / 26;
    Int32 secondLetter = column % 26;
    String columName = String.Empty;
    if (firstLetter > 25)
    {
        columName = GetExcelColumnLetters(firstLetter, true);
    }
    else if (firstLetter > 0)
    {
        columName = Convert.ToChar(firstLetter + 64).ToString();
    }
    columName += Convert.ToChar(secondLetter + 65).ToString();
    return (columName);
}


private static void TestGetExcelColumnLetters(Int32 column)
{
    String columName;

    columName = GetExcelColumnLetters(column, false);
    Console.WriteLine(columName);
    columName = GetExcelColumnLetters(column - 1, true);
    Console.WriteLine(columName);
}

static void Main()
{
    TestGetExcelColumnLetters(1);
    Console.WriteLine();
    TestGetExcelColumnLetters(5);
    Console.WriteLine();
    TestGetExcelColumnLetters(26);
    TestGetExcelColumnLetters(27);
    TestGetExcelColumnLetters(28);
    Console.WriteLine();
    TestGetExcelColumnLetters(52);
    TestGetExcelColumnLetters(53);
    Console.WriteLine();
    TestGetExcelColumnLetters(700);
    TestGetExcelColumnLetters(701);
    TestGetExcelColumnLetters(702);
    TestGetExcelColumnLetters(703);
    TestGetExcelColumnLetters(704);
    TestGetExcelColumnLetters(705);
    Console.ReadLine();
}