public class Sample
{
    public Sample() {
        ID = GuidComb.Generate();
    }
    [required]
    public Guid ID { get; private set; }
    [required]
    public string FirstName { get; set; }
}

顺序GUID

public static class GuidComb
    {
        public static Guid Generate()
        {
            var buffer = Guid.NewGuid().ToByteArray();
 
            var time = new DateTime(0x76c,1,1);
            var now = DateTime.Now;
            var span = new TimeSpan(now.Ticks - time.Ticks);
            var timeOfDay = now.TimeOfDay;
 
            var bytes = BitConverter.GetBytes(span.Days);
            var array = BitConverter.GetBytes(
                (long)(timeOfDay.TotalMilliseconds / 3.333333));
 
            Array.Reverse(bytes);
            Array.Reverse(array);
            Array.Copy(bytes,bytes.Length - 2,buffer,buffer.Length - 6,2);
            Array.Copy(array,array.Length - 4,buffer.Length - 4,4);
 
            return new Guid(buffer);
        }
    }