.NET Short Unique Identifier

Question

I need a unique identifier in .NET (cannot use GUID as it is too long for this case).

Do people think that the algorithm used here is a good candidate or do you have

Answer 1

If your app dont have a few MILLIION people, using that generate short unique string at the SAME MILLISECOND, you can think about using below function.

private static readonly Object obj = new Object();
private static readonly Random random = new Random();
private string CreateShortUniqueString()
{
    string strDate = DateTime.Now.ToString("yyyyMMddhhmmssfff");
    string randomString ;
    lock (obj)
    {
        randomString = RandomString(3);
    }
    return strDate + randomString; // 16 charater
}
private string RandomString(int length)
{

    const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxy";
    var random = new Random();
    return new string(Enumerable.Repeat(chars, length)
      .Select(s => s[random.Next(s.Length)]).ToArray());
}

change yyyy to yy if you just need to use your app in next 99 year.
Update 20160511: Correct Random function
- Add Lock object
- Move random variable out of RandomString function
Ref