HanSolo

Indeed I do love me regular expressions - and because of the "construct it once" mentality, I've taken to using them statically as much as possible. And that also lends them to being used in extension methods nicely:

namespace Aesop.Extensions
{
#region Using Directives

// System namespaces
using System.Text.RegularExpressions;

#endregion

#region Static Class Definition : EmailValidatorExtension

/// <summary>
/// Holds the IsValidEmailAddress () extension method.
/// </summary>
public static class EmailValidatorExtension
{
#region Public Static Extension Methods

/// <summary>
/// Determines whether the specified string is a valid email address.
/// </summary>
/// <param name="value">
/// The string to validate.
/// </param>
/// <returns>
/// <c>true</c> if the specified string is a valid email address;
/// otherwise, <c>false</c>.
/// </returns>
public static bool
IsValidEmailAddress (this string value)
{
return m_validEmail.IsMatch (value);
}

#endregion

#region Private Static Member Data

/// <summary>
/// The regular expression to test the string against.
/// </summary>
private static readonly Regex m_validEmail =
new Regex (
@"^(([^<>()[\]\\.,;:\s@\""]+"
+ @"(\.[^<>()[\]\\.,;:\s@\""]+)*)|(\"".+\""))@"
+ @"((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}"
+ @"\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+"
+ @"[a-zA-Z]{2,}))$",
RegexOptions.Compiled);

#endregion
}

#endregion
}