UK Postcode Implementation

Postcode.cs

namespace Diuturnal.Utility {
  [Serializable]
  public struct Postcode {
    private const string ValidationString =
      @"^\s*(?<out>[A-Z]{1,2}[0-9R][0-9A-Z]?) *(?<in>[0-9][A-Z-[CIKMOV]]{2})\s*$";
    private static readonly Regex _validator =
      new Regex(ValidationString);
    public static readonly Postcode Empty =
      new Postcode(string.Empty, string.Empty);
    private string _outCode;
    private string _inCode;

    private Postcode(string outCode, string inCode) {
      _outCode = outCode;
      _inCode = inCode;
    }

    public override string ToString() {
      if (0 == _outCode.Length) {
        return string.Empty;
      }
      return _outCode + " " + _inCode;
    }

    public override bool Equals(object obj) {
      if (!(obj is Postcode)) {
        return false;
      }
      return (this == (Postcode) obj);
    }

    public override int GetHashCode() {
      return this.ToString().GetHashCode();
    }

    public static bool operator ==(Postcode lhs, Postcode rhs) {
      return (lhs.ToString() == rhs.ToString());
    }

    public static bool operator !=(Postcode lhs, Postcode rhs) {
      return !(lhs == rhs);
    }

    public static Postcode Parse(string s) {
      if (null == s) {
        throw new ArgumentNullException();
      }
      string capitalised = s.ToUpper();
      if (!_validator.IsMatch(capitalised)) {
        throw new FormatException();
      }
      return new Postcode(_validator.Replace(capitalised, "${out}"),
        _validator.Replace(capitalised, "${in}"));
    }

    public static bool TryParse(string s, out Postcode result) {
      if (null == s) {
        result = Postcode.Empty;
        return false;
      }
      string capitalised = s.ToUpper();
      if (!_validator.IsMatch(capitalised)) {
        result = Postcode.Empty;
        return false;
      }
      result = new Postcode(_validator.Replace(capitalised, "${out}"),
        _validator.Replace(capitalised, "${in}"));
      return true;
    }
  }
}