Question

I have the a function I took from this post which works great:

private string GenerateTransactionCode()
{
    var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    var random = new Random();
    var result = new string(
        Enumerable.Repeat(chars, 8)
                  .Select(s => s[random.Next(s.Length)])
                  .ToArray());
    return result;
}

I would like to modify it so that instead of it being random, it picks the alpha numeric digits based on DateTime.UtcNow.Ticks. This way it will be non-repeating. I suppose the characters in the resulting TransactionCode might need to be increased depending on the length of the milliseconds? I would like the length of the resulting TransactionCode to be constant. Hopefully, no more than 8 Characters.

Example: If the ticks happened to be 135 (going to me more than that in real life) then the resulting code will be ACE or BDF depending if it’s 0 based (I don’t care if it is or not).

Answer 1

I imagine what you actually want is a real non-repeating transaction code, or GUID:

Guid g = Guid.NewGuid();
string txcode = Convert.ToBase64String(g.ToByteArray());

If you want to clean it up:

txcode = txcode.Replace("=","").Replace("+","").Replace("/","");

Example of generated output is OEndimZwsEKRAbAwnvzjoA but because of the replacement of + / and = the length can be slightly unpredictable.

You may prefer this format g.ToString("N") which gives something like 58d5381c878b484591568b086296fe8e and is guaranteed to be 32 characters long.