Is there any way to create a short unique code like short GUID?

Question

I want to create a short GUID. Is there any way to create a short unique code like short GUID? I want to create a ticket tracking number.

Answer 1

unique within one year, visibly 'random'

string UniqueID()
{
    var t = DateTime.UtcNow;
    long dgit = t.Millisecond   * 1000000000L +
                t.DayOfYear     * 1000000L +
                t.Hour          * 10000L +
                t.Minute        * 100L +
                t.Second;
    return Convert.ToBase64String(BitConverter.GetBytes(dgit).Take(5).ToArray()).TrimEnd('=');
}

here's one with a customizable character set

string UniqueID(string CharList = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ")
{
    var t = DateTime.UtcNow;
    char[] charArray = CharList.ToCharArray();
    var result = new Stack();

    var length = charArray.Length;

    long dgit = 1000000000000L +
                t.Millisecond   * 1000000000L +
                t.DayOfYear     * 1000000L +
                t.Hour          * 10000L +
                t.Minute        * 100L +
                t.Second;

    while (dgit != 0)
    {
        result.Push(charArray[dgit % length]);
        dgit /= length;
    }
    return new string(result.ToArray());
}