.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

    public static string ToTinyUuid(this Guid guid)
    {
        return Convert.ToBase64String(guid.ToByteArray())[0..^2]  // remove trailing == padding 
            .Replace('+', '-')                          // escape (for filepath)
            .Replace('/', '_');                         // escape (for filepath)
    }

Usage

Guid.NewGuid().ToTinyUuid()

It's not rocket science to convert back, so I'll leave you that much.

Answer 2

private static readonly object _getUniqueIdLock = new object();
public static string GetUniqueId()
{       
    lock(_getUniqueIdLock)
    {
        System.Threading.Thread.Sleep(1);
        return DateTime.UtcNow.Ticks.ToString("X");
    }
}

Answer 3

Based on @dorcohen's answer and @pootzko's comment. You can use this. It is safe over the wire.

var errorId = System.Web.HttpServerUtility.UrlTokenEncode(Guid.NewGuid().ToByteArray());

Answer 4

If you dont need to type the string you could use the following:

static class GuidConverter
{
    public static string GuidToString(Guid g)
    {
        var bytes = g.ToByteArray();
        var sb = new StringBuilder();
        for (var j = 0; j < bytes.Length; j++)
        {
            var c = BitConverter.ToChar(bytes, j);
            sb.Append(c);
            j++;
        }
        return sb.ToString();
    }

    public static Guid StringToGuid(string s) 
        => new Guid(s.SelectMany(BitConverter.GetBytes).ToArray());
}

This will convert the Guid to a 8 character String like this:

{b77a49a5-182b-42fa-83a9-824ebd6ab58d} --> "䦥띺ᠫ䋺ꦃ亂檽趵"

{c5f8f7f5-8a7c-4511-b667-8ad36b446617} --> "엸詼䔑架펊䑫ᝦ"

Answer 5

22 chars, url safe, and retains Guid uniqueness.

// Our url safe, base 64 alphabet:
const string alphabet = "-_0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

// Sanitized Guid string. Preserve the last two hex chars
var guidStr = "929F7C4D4B2644E1A122A379C02D6345";
var lastTwo = guidStr.Substring(30, 2);

string shortGuid = "";

// Iterate over the ten groups of 3 hex chars: 929 F7C 4D4 B26 44E 1A1 22A 379 C02 D63
for (var i = 0; i < 10; i++)
{
    var hex = guidStr.Substring(i*3, 3);              // Get the next 3 hex chars
    var x = Convert.ToInt32(hex, 16);                 // Convert to int
    shortGuid += $"{alphabet[x/64]}{alphabet[x%64]}"; // Lookup the two-digit base64 value
}
shortGuid += lastTwo; // Don't forget the last two

Console.WriteLine(shortGuid);

Output:

yDXWhiGAfc4v6EbTK0Px45

Answer 6

For my local app I'm using this time based approach:

/// <summary>
/// Returns all ticks, milliseconds or seconds since 1970.
/// 
/// 1 tick = 100 nanoseconds
/// 
/// Samples:
/// 
/// Return unit     value decimal           length      value hex       length
/// --------------------------------------------------------------------------
/// ticks           14094017407993061       17          3212786FA068F0  14
/// milliseconds    1409397614940           13          148271D0BC5     11
/// seconds         1409397492              10          5401D2AE        8
///
/// </summary>
public static string TickIdGet(bool getSecondsNotTicks, bool getMillisecondsNotTicks, bool getHexValue)
{
    string id = string.Empty;

    DateTime historicalDate = new DateTime(1970, 1, 1, 0, 0, 0);

    if (getSecondsNotTicks || getMillisecondsNotTicks)
    {
        TimeSpan spanTillNow = DateTime.UtcNow.Subtract(historicalDate);

        if (getSecondsNotTicks)
            id = String.Format("{0:0}", spanTillNow.TotalSeconds);
        else
            id = String.Format("{0:0}", spanTillNow.TotalMilliseconds);
    }
    else
    {
        long ticksTillNow = DateTime.UtcNow.Ticks - historicalDate.Ticks;
        id = ticksTillNow.ToString();
    }

    if (getHexValue)
        id = long.Parse(id).ToString("X");

    return id;
}