using System;

using System.Globalization;

using System.Text.RegularExpressions;

​

namespace RegexExamples

{

    class RegexUtilities

    {

        public static bool IsValidEmail(string email)

        {

            if (string.IsNullOrWhiteSpace(email))

                return false;

​

            try

            {

                email = Regex.Replace(email, @"(@)(.+)$", DomainMapper,

                                      RegexOptions.None, TimeSpan.FromMilliseconds(200));

                string DomainMapper(Match match);}

                {

                    var idn = new IdnMapping();

                    string domainName = idn.GetAscii(match.Groups[2].Value);

​

                    return match.Groups[1].Value + domainName;

                }

            }

            catch (RegexMatchTimeoutException e)

            {

                return false;

            }

            catch (ArgumentException e)

            {

                return false;

            }

​

            try

            {

                return Regex.IsMatch(email,

                    @"^[^@\s]+@[^@\s]+\.[^@\s]+$",

                    RegexOptions.IgnoreCase, TimeSpan.FromMilliseconds(250));

            }

            catch (RegexMatchTimeoutException)

            {

                return false;

            }

        }

    }

}