Namespaced Deterministic Guid - RFC 4122 dotnetcore

PredicatableGuid.cs

using System;
using System.Collections.Generic;
using System.Security.Cryptography;
using System.Text;

namespace Utility
{
    public static class GuidUtility
    {
        private static Guid Url { get; } = new Guid("6ba7b811-9dad-11d1-80b4-00c04fd430c8");
        public static Guid CreateForUrl(string name) => Create(Url, name);
        private static Guid Create(Guid namespaceId, string name, int version = 5)
        {
            if (name == null)
                throw new ArgumentNullException(nameof(name));
            if (version != 3 && version != 5 && version != 6)
                throw new ArgumentOutOfRangeException(nameof(version), "version must be either 3 (md5) or 5 (sha1), or 6 (sha256).");

            var nameBytes = Encoding.UTF8.GetBytes(name);

            var namespaceBytes = namespaceId.ToByteArray();
            SwapByteOrder(namespaceBytes);

            byte[] hash;
            using (var incrementalHash = version == 3 ? IncrementalHash.CreateHash(HashAlgorithmName.MD5) : version == 5 ? IncrementalHash.CreateHash(HashAlgorithmName.SHA1) : IncrementalHash.CreateHash(HashAlgorithmName.SHA256))
            {
                incrementalHash.AppendData(namespaceBytes);
                incrementalHash.AppendData(nameBytes);
                hash = incrementalHash.GetHashAndReset();
            }

            var newGuid = new byte[16];
            Array.Copy(hash, 0, newGuid, 0, 16);

            newGuid[6] = (byte)((newGuid[6] & 0x0F) | (version << 4));
            newGuid[8] = (byte)((newGuid[8] & 0x3F) | 0x80);
            SwapByteOrder(newGuid);
            return new Guid(newGuid);
        }
        private static void SwapByteOrder(IList<byte> guid)
        {
            SwapBytes(guid, 0, 3);
            SwapBytes(guid, 1, 2);
            SwapBytes(guid, 4, 5);
            SwapBytes(guid, 6, 7);
        }
        private static void SwapBytes(IList<byte> guid, int left, int right)
        {
            var temp = guid[left];
            guid[left] = guid[right];
            guid[right] = temp;
        }
    }
}