using System;

public class Program

{

public static void Main()

{

    var guid = NewGuid(84418896782855,10027);

    Console.WriteLine(guid);

}

public static Guid NewGuid(long? uid, int? clientId)

{

    if (!uid.HasValue || !clientId.HasValue)

    {

        return Guid.Empty;

    }

    var bytes = new byte[16];

    BitConverter.GetBytes(uid.Value).CopyTo(bytes, 0);

    BitConverter.GetBytes(clientId.Value).CopyTo(bytes, 12);

    return new Guid(bytes);

}

}

​

​

​

​