using System;

public class Program

{

    public void Main()

    {

        ulong test = 123;

        Console.WriteLine(ToGuid(test));

​

        test = 804689000304;

        Console.WriteLine(ToGuid(test));

​

        test = 11003050607091;

        Console.WriteLine(ToGuid(test));

​

        test = ulong.MaxValue;

        Console.WriteLine(ToGuid(test));

        Console.WriteLine(123.ToString("00"));

​

        Console.WriteLine(ulong.MaxValue.ToString("00000000-0000-0000-0000-000000000000"));

​

        var guid = new Guid(ulong.MaxValue.ToString("00000000-0000-0000-0000-000000000000"));

        Console.WriteLine(guid);

        Console.WriteLine(guid.ToString("N"));

        Console.WriteLine(Convert.ToUInt64(guid.ToString("N")));

    }

    private string ToGuid(ulong value)

    {

        //654B9E89-9997-4D67-9316-7EC2FDFF29CD

​

        var tail = value % 1000000000000;

        string result = "-"+tail.ToString("000000000000");

​

        tail = (value / 1000000000000) % 1000;

        result = "-" + tail.ToString("0000") + result;

​

        tail = value / 10000000000000000;

        result = "00000000-0000-" + tail.ToString("0000") + result;

​

        return result;

    }

}

​