using System;

using System.Text.RegularExpressions;

using System.Globalization;

public class Program

{

    public static void Main()

    {

        string[] emailAddresses = { "david.jones@proseware.com", "d.j@server1.proseware.com",

                                    "jones@ms1.proseware.com", "j.@server1.proseware.com",

                                    "j@proseware.com9", "js#internal@proseware.com",

                                    "j_9@[129.126.118.1]", "j..s@proseware.com",

                                    "js*@proseware.com", "js@proseware..com",

                                    "js@proseware.com9", "j.s@server1.proseware.com",

                                    "\"j\\\"s\\\"\"@proseware.com", "js@contoso.中国", "js@contoso.com?" };

​

        foreach (var emailAddress in emailAddresses)

        {

            if (IsValidEmail(emailAddress))

                Console.WriteLine("Valid:   {emailAddress}");

            else

                Console.WriteLine("Invalid: {emailAddress}");

        }

​

    }

     public static bool IsValidEmail(string strIn)

        {

            //try

            //{

            //    System.Net.Mail.MailAddress tryIt = new System.Net.Mail.MailAddress(strIn);

            //    return true;

            //}

            //catch { return false; }

            /*

            http://msdn.microsoft.com/en-us/library/01escwtf(v=vs.110).aspx

            */

​

            bool invalid = false;

            invalid = false;

            if (String.IsNullOrEmpty(strIn))

                return false;

​

            // Use IdnMapping class to convert Unicode domain names.

            strIn = Regex.Replace(strIn, @"(@)(.+)$", DomainMapper, RegexOptions.None);

            if (invalid)

                return false;

​

            // Return true if strIn is in valid e-mail format.

            return Regex.IsMatch(strIn,

                   @"^(?("")("".+?(?<!\\)""@)|(([0-9a-z]((\.(?!\.))|[-!#\$%&'\*\+/=\?\^`\{\}\|~\w])*)(?<=[0-9a-z])@))" +

                   @"(?(\[)(\[(\d{1,3}\.){3}\d{1,3}\])|(([0-9a-z][-\w]*[0-9a-z]*\.)+[a-z0-9][\-a-z0-9]{0,22}[a-z0-9]))$",

                   RegexOptions.IgnoreCase);

        }

     private static string DomainMapper(Match match)

        {

            //bool invalid = false;

            // IdnMapping class with default property values.

            IdnMapping idn = new IdnMapping();

​

            string domainName = match.Groups[2].Value;

            try

            {

                domainName = idn.GetAscii(domainName);

            }

            catch (ArgumentException)

            {

                //invalid = true;

            }

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

        }

}