CompactGuid.cs

using System;

namespace TCastr.Models
{
  /// <summary>
  /// An implicitly-convertible buffer that automatically converts between
  /// a compact string representation and a Guid.
  /// </summary>
  /// <remarks>
  /// Reference implementation:
  /// http://www.singular.co.nz/blog/archive/2007/12/20/shortguid-a-shorter-and-url-friendly-guid-in-c-sharp.aspx
  /// </remarks>
  public struct CompactGuid
  {
    private Guid _guid = Guid.Empty;
    private string _str = null;


    public Guid Guid { get { return this; } }

    private CompactGuid() { _guid = Guid.NewGuid(); }
    public CompactGuid(string s) { _str = s; }
    public CompactGuid(Guid guid) { _guid = guid; }


    public static CompactGuid NewGuid()
    {
      return Guid.NewGuid();
    }


    public static implicit operator CompactGuid(string source) { return new CompactGuid(source); }
    public static implicit operator CompactGuid(Guid source) { return new CompactGuid(source); }

    public static implicit operator string(CompactGuid source)
    {
      return (source._guid != null) ? Encode(source._guid) : source._str;
    }

    public static implicit operator Guid(CompactGuid source)
    {
      return (source._guid != null) ? source._guid : Decode(source._str);
    }


    public static string Encode(Guid guid)
    {
      return Convert
        .ToBase64String(guid.ToByteArray())
        .Replace('/', '_')
        .Replace('+', '-')
        .Substring(0, 22);
    }

    public static Guid Decode(string sguid)
    {
      return new Guid(Convert.FromBase64String(sguid
        .Replace('-', '+')
        .Replace('_', '/')
        + "=="));
    }


    public override string ToString() { return this; }
  }
}