Creates GUID combs

GuidHelper.cs

using System;

namespace Terabyte.Data
{
	/// <summary>Guid utilities</summary>
	public static class GuidHelper
	{
		/// <summary>Given a string returns a Guid. </summary>
		/// <remarks> Returns <c>Guid.Empty</c> if s is null.</remarks>
		/// <param name="s">Any parsable guid, or the return value from <see cref="GuidToString"/></param>
		/// <returns>A Guid you ninny!</returns>
		/// <exception cref="ArgumentException">Thrown if s cannot be converted to a guid.</exception>
		public static Guid StringToGuid(string s) 
		{
			if (string.IsNullOrEmpty(s))
				throw new ArgumentException(string.Format("Could not create Guid from empty or null string", s), "s");

			try 
			{
				if (s.Length == 22) 
				{
					s = s.Replace('!', '/').Replace('*', '/').Replace('_', '/').Replace("-", "+") + "==";
					return new Guid(Convert.FromBase64String(s));
				}
			
				return new Guid(s);
			} 
			catch(FormatException) 
			{
				throw new ArgumentException(string.Format("Could not create Guid from string '{0}'", s), "s");
			}
		}

		/// <summary>
		/// Returns a compressed string representation of a guid, which can be 
		/// extracted again by calling <see cref="GuidHelper.StringToGuid(string)"/>
		/// </summary>
		/// <remarks>
		///	Implementation: 
		///	<code>return Convert.ToBase64String(g.ToByteArray()).Substring(0, 22).Replace('/', '*');</code>
		/// </remarks>
		/// <param name="g"></param>
		/// <returns></returns>
		public static string GuidToString(Guid g) 
		{
			return Convert.ToBase64String(g.ToByteArray()).Substring(0, 22).Replace('/', '_').Replace("+", "-");
		}

		/// <summary>Creates a database friendly guid (http://www.informit.com/articles/article.aspx?p=25862)</summary>
		/// <returns></returns>
		public static Guid NewDatabaseGuid()
		{
			long dateTicks = DateTime.Now.Ticks;
			return GenerateSequenceGuid(dateTicks, 0);
		}
		
		public static Guid GenerateSequenceGuid(long sequenceNumber, byte guidVersion)
		{
			Guid baseGuid = Guid.NewGuid();
			byte[] guidData = baseGuid.ToByteArray();
			guidData[15] = (byte )((sequenceNumber >> 0) & 0xFF);
			guidData[14] = (byte )((sequenceNumber >> 8) & 0xFF);
			guidData[13] = (byte )((sequenceNumber >> 16) & 0xFF);
			guidData[12] = (byte )((sequenceNumber >> 24) & 0xFF);
			guidData[11] = (byte )((sequenceNumber >> 32) & 0xFF);
			guidData[10] = (byte )((sequenceNumber >> 48) & 0xFF);

			guidData[8] = (byte )((guidData[8] & ~(0x3)) + guidVersion);
			
			return new Guid(guidData);
		}
	}
}