SSN Validation Regex

RegexPatterns.cs

public class RegexPatterns
{
    /// <summary>
    ///   Regular expression used to validate an US Social Security Number (SSN)
    ///   formatted as nine-digits with hyphens (###-##-####).
    /// </summary>
    /// <example>
    ///   <code>
    ///       var ssnRegex = new Regex(RegexPatterns.Ssn);
    ///       ssnRegex.IsMatch("078-05-1120"); // should return false
    ///   </code>
    /// </example>
    // TODO: should other consecutive numbers fail (ex. 234-56-7890)?
    public static readonly string Ssn
        // cannot be: 078-05-1120 (Woolworth advertising - https://www.ssa.gov/history/ssn/misused.html),
        //            123-45-6789 (sequential digits),
        //            219-09-9999 (SSA advertising from 1940),
        //            457-55-5462 (LifeLock CEO's SSN),
        //            nor 721-07-4426 (1943 deceased and shown in Wikipedia)
        = "(?!078-05-1120|123-45-6789|219-09-9999|457-55-5462|721-07-4426)"
            // cannot be all the same digit (e.g. 555-55-5555)
            + @"(?!\b([0-9])\1+-([0-9])\1+-([0-9])\1+\b)"
            + "(?!000|666|9)"   // cannot start with 000, 666 or 900-999
            + "[0-9]{3}-"       // must start with 3 digits followed by a dash
            + "(?!00)"          // cannot be 00
            + "[0-9]{2}-"       // must be 2 digits followed by a dash
            + "(?!0{4})"        // cannot be 0000
            + "[0-9]{4}";       // end end string

    /// <summary>
    ///   Regular expression used to validate an US Social Security Number (SSN)
    ///   formatted as nine-digits with no hyphens (#########).
    /// </summary>
    public static readonly string SsnWithNoDashes
        = Ssn.Replace("-", "").Replace("[09]", "[0-9]");

    /// <summary>
    ///   Regular expression used to validate an US Social Security Number (SSN)
    ///   formatted as nine-digits with "optional" hyphens (#########, ###-######, #####-#### or ###-##-####).
    /// </summary>
    public static readonly string SsnWithOptionalDashes
        = Ssn.Replace("-", "-?").Replace("[0-?9]", "[0-9]");
}