using System;

using System.Text;

using System.Security.Cryptography;

​

public class Program

{

    public static readonly Guid StockNamespace = new Guid("a305265f-9b07-4204-9eec-f674bd7d7471");

    public static void Main()

    {

        Console.WriteLine(CreateStockIdentity("NX18XUY",Guid.Parse("a6a3e838-dce4-4fa1-bda8-5114f89a42f0")));

    }

​

    public static Guid CreateStockIdentity(string vrm, Guid dealerId)

    {

        return Create(StockNamespace, vrm + dealerId);

    }

​

    public static Guid Create(Guid namespaceId, string name)

    {

        return Create(namespaceId, name, 6);

    }

​

    public static Guid Create(Guid namespaceId, string name, int version)

    {

        if (name == null)

            throw new ArgumentNullException("name");

        if (version != 3 && version != 5 && version != 6)

            throw new ArgumentOutOfRangeException("version", "version must be either 3 (md5) or 5 (sha1), or 6 (sha256).");

        // convert the name to a sequence of octets (as defined by the standard or conventions of its namespace) (step 3)

        // ASSUME: UTF-8 encoding is always appropriate

        byte[] nameBytes = Encoding.UTF8.GetBytes(name);

        // convert the namespace UUID to network order (step 3)

        byte[] namespaceBytes = namespaceId.ToByteArray();

        SwapByteOrder(namespaceBytes);

        // comput the hash of the name space ID concatenated with the name (step 4)

        byte[] hash;

        //using (HashAlgorithm algorithm = version == 3 ? (HashAlgorithm)MD5.Create() : SHA1.Create())

        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();

        // algorithm.TransformBlock(namespaceBytes, 0, namespaceBytes.Length, null, 0);

        // algorithm.TransformFinalBlock(nameBytes, 0, nameBytes.Length);

        //hash = algorithm.Hash;

        }

​

        // most bytes from the hash are copied straight to the bytes of the new GUID (steps 5-7, 9, 11-12)

        byte[] newGuid = new byte[16];

        Array.Copy(hash, 0, newGuid, 0, 16);

        // set the four most significant bits (bits 12 through 15) of the time_hi_and_version field to the appropriate 4-bit version number from Section 4.1.3 (step 8)

        newGuid[6] = (byte)((newGuid[6] & 0x0F) | (version << 4));

        // set the two most significant bits (bits 6 and 7) of the clock_seq_hi_and_reserved to zero and one, respectively (step 10)

        newGuid[8] = (byte)((newGuid[8] & 0x3F) | 0x80);

        // convert the resulting UUID to local byte order (step 13)

        SwapByteOrder(newGuid);

        return new Guid(newGuid);

    }

​

    private static void SwapByteOrder(byte[] guid)

    {

        SwapBytes(guid, 0, 3);

        SwapBytes(guid, 1, 2);

        SwapBytes(guid, 4, 5);

        SwapBytes(guid, 6, 7);

    }

​

    private static void SwapBytes(byte[] guid, int left, int right)

    {

        byte temp = guid[left];

        guid[left] = guid[right];

        guid[right] = temp;

    }

}