C# Check if email address is valid using regular expressions

using System.Text.RegularExpressions;

/// <summary>
/// Determines whether source is a valid email address.
/// </summary>
/// <param name="source">The source</param>
/// <returns>
///   <c>true</c> if source is valid email address; otherwise, <c>false</c>.
/// </returns>
public static bool IsValidEmailAddress(this string source)
{
    Regex regex = new Regex(@"^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$");
    return regex.IsMatch(source);
}