How to generate 8 byte GUID value in c#? [duplicate]

Answer 1

With an 8 byte value (64 bits) you will have 2^64 possible outcomes. That's quite a few but significantly less than a GUID which has 2 ^ 128 possible values.

You could do something this simple:

        // generate 8 byte random value
        Random rnd = new Random();
        byte[] bytes = new byte[8];
        rnd.NextBytes(bytes);

        // displaying the value
        string myRndID = BitConverter.ToString(bytes).Replace("-", "");
        Console.WriteLine(myRndID);

For example:

XXXX           YY        ZZ
----           --        --
Random Value   Node ID   Days since epoch (of your definition)

Then:

Cat XXXX, YY and ZZ bytes together to create your pseudo-guID.

But that approach uses only random number generation. You could take a hint from the GUID algorithms (current and past) and populate some of the 8 bytes with a node ID value or a DateTime hash or something such combined with a random value to reduce the risk of collisions.

Still, the potential for collisions is there and if you do end up using an 8 byte pseudo-guID you should have a process defined for handling a collision.