in c#, how can i build up array from A to ZZ that is similar to the way that excel orders columns

Question

i am looking for code that can generate an array where the first item is A, then B, then C . . .after Z i

Answer 1

To complement Vlad's answer, here's the reverse operation of ToBase26(int):

static long ToBase10(string str)
{
   if (string.IsNullOrWhiteSpace(str)) return 0;
   var value = str[0] - 'A' + 1;

   return (long) (value * Math.Pow(26, str.Length - 1) + 
          ToBase10(str.Substring(1, str.Length - 1)));
}

Answer 2

Here's one way. :)

string[] values =
  Enumerable.Range(0, 27 * 26)
  .Select(
    n => new String(
      new[] { (char)('@' + n / 26), (char)('A' + n % 26) },
      n < 26 ? 1 : 0, n < 26 ? 1 : 2
    )
  )
  .ToArray();

Answer 3

class Program
{
    public static string IntegerToExcelColumn(int col)
    {
        // I've put a 256 upper bound here because Excel 2003 
        // allows only 256 columns. Change it if you're using 
        // Excel 2007 or 2010.
        Debug.Assert(col >= 1 && col <= 256);

        if (col >= 1 && col <= 26)
        {
            return ((char)(((int)'A') + (col - 1))).ToString();
        }

        // I've put a 256 upper bound here because Excel 2003 
        // allows only 256 columns. Change it if you're using 
        // Excel 2007 or 2010.
        if (col > 26 && col <= 256)
        {
            int rem = col % 26;
            int pri = col / 26;
            if (rem == 0)
            {
                rem = 26;
                pri--;
            }
            char[] buffer = new char[2];
            buffer[0] = (char)(((int)'A') + (pri - 1));
            buffer[1] = (char)(((int)'A') + (rem - 1));
            return new string(buffer);
        }

        return "";
    }

    static void Main(string[] args)
    {
        string[] columns= new string[255];
        for (int i = 1; i <= 255; i++)
            columns[i-1] = IntegerToExcelColumn(i);
        foreach(var col in columns)
            Console.WriteLine(col);
    }
}

Answer 4

Have a look at an ASCII table and take note of the values of the characters. You should be able to work out a loop to increment the character from A to Z for as many times as you need to replicate the characters. :)

Answer 5

One of the ways is:

IEnumerable<string> generate()
{
    for (char c = 'A'; c <= 'Z'; c++)
        yield return new string(c, 1);
    for (char c = 'A'; c <= 'Z'; c++)
        for (char d = 'A'; d <= 'Z'; d++)
            yield return new string(new[] { c, d });
}

---

Edit:
you can actually produce "infinite" sequence (bounded by maximal long value) with somewhat more complicated code:

string toBase26(long i)
{
    if (i == 0) return ""; i--;
    return toBase26(i / 26) + (char)('A' + i % 26);
}

IEnumerable<string> generate()
{
    long n = 0;
    while (true) yield return toBase26(++n);
}

This one goes like that: A, B, ..., Z, AA, AB, ..., ZZ, AAA, AAB, ... etc:

foreach (var s in generate().Take(200)) Console.WriteLine(s);

Answer 6

You could generate numbers using Enumerable.Range and cast them to char to generate A-Z. Next step is to combine them.