C code to validate email address

Question

What is the most elegant code to validate that a string is a valid email address

User · Answer

I wrote an function to check if an email is valid or not. It seems working well for me in most cases.

Results:

[email protected] => FALSE
[email protected] => FALSE
[email protected] => FALSE
[email protected] => FALSE
[email protected] => FALSE
dad@sds => FALSE
[email protected] => FALSE
[email protected] => FALSE
asd@[email protected] => FALSE
[email protected] => FALSE
[email protected] => FALSE

[email protected] => TRUE
[email protected] => TRUE
[email protected] => TRUE
[email protected] => TRUE

Code:

    private bool IsValidEmail(string email)
    {
        bool valid = false;
        try
        {
            var addr = new System.Net.Mail.MailAddress(email);
            valid = true;
        }
        catch
        {
            valid = false;
            goto End_Func;
        }

        valid = false;
        int pos_at = email.IndexOf('@');
        char checker = Convert.ToChar(email.Substring(pos_at + 1, 1));
        var chars = "qwertyuiopasdfghjklzxcvbnm0123456789";
        foreach (char chr in chars)
        {
            if (checker == chr)
            {
                valid = true;
                break;
            }
        }
        if (valid == false)
        {
            goto End_Func;
        } 

        int pos_dot = email.IndexOf('.', pos_at + 1);
        if(pos_dot == -1)
        {
            valid = false;
            goto End_Func;
        }

        valid = false;
        try
        {
            checker = Convert.ToChar(email.Substring(pos_dot + 1, 1));
            foreach (char chr in chars)
            {
                if (checker == chr)
                {
                    valid = true;
                    break;
                }
            }
        }
        catch
        {
            valid = false;
            goto End_Func;
        }

        Regex valid_checker = new Regex(@"^[[email protected]]*$");
        valid = valid_checker.IsMatch(email);
        if (valid == false)
        {
            goto End_Func;
        }

        List<int> pos_list = new List<int> { };
        int pos = 0;
        while (email.IndexOf('_', pos) != -1)
        {
            pos_list.Add(email.IndexOf('_', pos));
            pos = email.IndexOf('_', pos) + 1;
        }

        pos = 0;
        while (email.IndexOf('.', pos) != -1)
        {
            pos_list.Add(email.IndexOf('.', pos));
            pos = email.IndexOf('.', pos) + 1;
        }

        pos = 0;
        while (email.IndexOf('-', pos) != -1)
        {
            pos_list.Add(email.IndexOf('-', pos));
            pos = email.IndexOf('-', pos) + 1;
        }

        int sp_cnt = pos_list.Count();
        pos_list.Sort();
        for (int i = 0; i < sp_cnt - 1; i++)
        {
            if (pos_list[i] + 1 == pos_list[i + 1])
            {
                valid = false;
                break;
            }

            if (pos_list[i]+1 == pos_at || pos_list[i]+1 == pos_dot)
            {
                valid = false;
                break;
            }
        }

        if(valid == false)
        {
            goto End_Func;
        }

        if (pos_list[sp_cnt - 1] == email.Length - 1 || pos_list[0] == 0)
        {
            valid = false;
        }

    End_Func:;
        return valid;
    }

User · Answer

I succinctified Poyson 1 s answer like so   public static bool IsValidEmailAddress string candidateEmailAddr        string regexExpresion      w   -      w      w   -    w        w   -    w          return  Regex IsMatch candidateEmailAddr  regexExpresion    amp  amp               Regex Replace candidateEmailAddr  regexExpresion  string Empty  Length    0

User · Answer

I created an email address validation routine based on Wikipedia s documented rules and sample addresses  For those that don t mind looking at a little more code  here you go  Honestly  I had no idea how many crazy rules there were in the email address specification  I don t fully validate the hostname or ipaddress  but it still passes all of the test cases on wikipedia   using Microsoft VisualStudio TestTools UnitTesting   namespace EmailValidateUnitTests        TestClass      public class EmailValidationUnitTests                TestMethod          public void TestEmailValidate                            Positive Assertions             Assert IsTrue  prettyandsimple example com  IsValidEmailAddress                 Assert IsTrue  very common example com  IsValidEmailAddress                 Assert IsTrue  disposable style email with symbol example com  IsValidEmailAddress                 Assert IsTrue  other email-with-dash example com  IsValidEmailAddress                 Assert IsTrue    much more unusual   example com  IsValidEmailAddress                 Assert IsTrue    very unusual   unusual com   example com  IsValidEmailAddress        very unusual   unusual com  example com             Assert IsTrue    very       lt  gt        VERY     very          very     unusual   strange example com  IsValidEmailAddress        very       lt  gt      VERY   very      very   unusual  strange example com             Assert IsTrue  admin mailserver1  IsValidEmailAddress                 Assert IsTrue       amp    -           example org  IsValidEmailAddress                 Assert IsTrue       lt  gt                    amp    -            a   example org  IsValidEmailAddress           lt  gt                amp    -            a  example org             Assert IsTrue        example org  IsValidEmailAddress           example org  space between the quotes              Assert IsTrue  example localhost  IsValidEmailAddress                 Assert IsTrue  example s solutions  IsValidEmailAddress                 Assert IsTrue  user com  IsValidEmailAddress                 Assert IsTrue  user localserver  IsValidEmailAddress                 Assert IsTrue  user  IPv6 2001 db8  1   IsValidEmailAddress                 Assert IsTrue  user  192 168 2 1   IsValidEmailAddress                 Assert IsTrue   comment and stuff joe gmail com  IsValidEmailAddress                 Assert IsTrue  joe comment and stuff  gmail com  IsValidEmailAddress                 Assert IsTrue  joe  comment and stuff gmail com  IsValidEmailAddress                 Assert IsTrue  joe gmail com comment and stuff   IsValidEmailAddress                     Failure Assertions             Assert IsFalse  joe fail me smith gmail com  IsValidEmailAddress                 Assert IsFalse  joesmith gma fail me il com  IsValidEmailAddress                 Assert IsFalse  joe gmail com comment and stuff  IsValidEmailAddress                 Assert IsFalse  Abc example com  IsValidEmailAddress                 Assert IsFalse  A b c example com  IsValidEmailAddress                 Assert IsFalse  a  b c d e f g lt h gt i j  k l example com  IsValidEmailAddress       a b c d e f g lt h gt i j k l example com             Assert IsFalse  just  not  right example com  IsValidEmailAddress       just not right example com             Assert IsFalse  this is  not  allowed example com  IsValidEmailAddress       this is not allowed example com             Assert IsFalse  this   still    not    allowed example com  IsValidEmailAddress      this  still  not  allowed example com             Assert IsFalse  john  doe example com  IsValidEmailAddress                 Assert IsFalse  john doe example  com  IsValidEmailAddress                 Assert IsFalse   joe gmail com  IsValidEmailAddress                 Assert IsFalse  joe gmail com   IsValidEmailAddress                          public static class ExtensionMethods               private const string ValidLocalPartChars    ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789     amp    -                     private const string ValidQuotedLocalPartChars          lt  gt                 private const string ValidDomainPartChars    ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-             private enum EmailParseMode                       BeginLocal  Local  QuotedLocalEscape  QuotedLocal  QuotedLocalEnd  LocalSplit  LocalComment              At              Domain  DomainSplit  DomainComment  BracketedDomain  BracketedDomainEnd                     public static bool IsValidEmailAddress this string s                        bool valid   true               bool hasLocal   false  hasDomain   false              int commentStart   -1  commentEnd   -1              var mode   EmailParseMode BeginLocal              for  int i   0  i  lt  s Length  i                                  char c   s i                   if  mode    EmailParseMode BeginLocal    mode    EmailParseMode LocalSplit                                        if  c           mode   EmailParseMode LocalComment  commentStart   i  commentEnd   -1                        else if  c           mode   EmailParseMode QuotedLocal                        else if  ValidLocalPartChars IndexOf c   gt   0    mode   EmailParseMode Local  hasLocal   true                        else   valid   false  break                                      else if  mode    EmailParseMode LocalComment                                        if  c                                                       mode   EmailParseMode Local  commentEnd   i                             comments can only be at beginning and end of parts                            if  commentStart    0  amp  amp    commentEnd   1   lt  s Length   amp  amp  s commentEnd   1            valid   false  break                                                            else if  mode    EmailParseMode Local                                        if  c         mode   EmailParseMode LocalSplit                      else if  c         mode   EmailParseMode At                      else if  c           mode   EmailParseMode LocalComment  commentStart   i  commentEnd   -1                        else if  ValidLocalPartChars IndexOf c   gt   0    hasLocal   true                        else   valid   false  break                                      else if  mode    EmailParseMode QuotedLocal                                        if  c           mode   EmailParseMode QuotedLocalEnd                        else if  c            mode   EmailParseMode QuotedLocalEscape                        else if  ValidLocalPartChars IndexOf c   gt   0    ValidQuotedLocalPartChars IndexOf c   gt   0    hasLocal   true                        else   valid   false  break                                      else if  mode    EmailParseMode QuotedLocalEscape                                        if  c           c            mode   EmailParseMode QuotedLocal  hasLocal   true                        else   valid   false  break                                      else if  mode    EmailParseMode QuotedLocalEnd                                        if  c           mode   EmailParseMode LocalSplit                        else if  c         mode   EmailParseMode At                      else if  c           mode   EmailParseMode LocalComment  commentStart   i  commentEnd   -1                        else   valid   false  break                                      else if  mode    EmailParseMode At                                        if  c           mode   EmailParseMode BracketedDomain                        else if  c           mode   EmailParseMode DomainComment  commentStart   i  commentEnd   -1                        else if  ValidDomainPartChars IndexOf c   gt   0    mode   EmailParseMode Domain  hasDomain   true                        else   valid   false  break                                      else if  mode    EmailParseMode DomainComment                                        if  c                                                       mode   EmailParseMode Domain                          commentEnd   i                             comments can only be at beginning and end of parts                            if   commentEnd   1     s Length  amp  amp   commentStart  gt  0   amp  amp  s commentStart - 1            valid   false  break                                                            else if  mode    EmailParseMode DomainSplit                                        if  ValidDomainPartChars IndexOf c   gt   0    mode   EmailParseMode Domain  hasDomain   true                        else   valid   false  break                                      else if  mode    EmailParseMode Domain                                        if  c           mode   EmailParseMode DomainComment  commentStart   i  commentEnd   -1                        else if  c           mode   EmailParseMode DomainSplit                        else if  ValidDomainPartChars IndexOf c   gt   0    hasDomain   true                        else   valid   false  break                                      else if  mode    EmailParseMode BracketedDomain                                        if  c           mode   EmailParseMode BracketedDomainEnd                        else if  c           ValidDomainPartChars IndexOf c   gt   0    hasDomain   true                        else   valid   false  break                                      else if  mode    EmailParseMode BracketedDomain                                        if  c           mode   EmailParseMode DomainComment  commentStart   i  commentEnd   -1                        else   valid   false  break                                                bool unfinishedComment    commentEnd    -1  amp  amp  commentStart  gt   0                return hasLocal  amp  amp  hasDomain  amp  amp  valid  amp  amp   unfinishedComment

User · Answer

There is culture problem in regex in C  rather then js  So we need to use regex in US mode for email check  If you don t use ECMAScript mode  your language special characters are imply in A-Z with regex   Regex IsMatch email       a-zA-Z0-9  -           0-9  1 3    0-9  1 3    0-9  1 3        a-zA-Z0-9  -          a-zA-Z  2 4   0-9  1 3           RegexOptions ECMAScript

User · Answer

A simple one without using Regex  which I don t like for its poor readability    bool IsValidEmail string email        string emailTrimed   email Trim         if   string IsNullOrEmpty emailTrimed                 bool hasWhitespace   emailTrimed Contains                int indexOfAtSign   emailTrimed LastIndexOf                if  indexOfAtSign  gt  0  amp  amp   hasWhitespace                        string afterAtSign   emailTrimed Substring indexOfAtSign   1                int indexOfDotAfterAtSign   afterAtSign LastIndexOf                    if  indexOfDotAfterAtSign  gt  0  amp  amp  afterAtSign Substring indexOfDotAfterAtSign  Length  gt  1                  return true                       return false      Examples    IsValidEmail   b com      false IsValidEmail  a  com      false IsValidEmail  a bcom      false IsValidEmail  a b com      false IsValidEmail  a b       false IsValidEmail  a b c com      false IsValidEmail  a b c com      false IsValidEmail  a b com      true  IsValidEmail  a b c com      true  IsValidEmail  a b c com      true IsValidEmail  a 123 45 67 89      true   It is meant to be simple and therefore it doesn t deal with rare cases like emails with bracketed domains that contain spaces  typically allowed   emails with IPv6 addresses  etc

User · Answer

I find this regex to be a good trade off between checking for something more than just the   mark  and accepting weird edge cases        s       s         s        It will at least make you put something around the   mark  and put at least a normal looking domain

User · Answer

Here is an answer to your question for you to check   using System  using System Globalization  using System Text RegularExpressions   public class RegexUtilities          public bool IsValidEmail string strIn              if  String IsNullOrEmpty strIn                      return false                       Use IdnMapping class to convert Unicode domain names          try                     strIn   Regex Replace strIn               this DomainMapper  RegexOptions None  TimeSpan FromMilliseconds 200                     catch  RegexMatchTimeoutException                       return false                    if  invalid                      return false                       Return true if strIn is in valid e-mail format              try                     return Regex IsMatch strIn                    lt             0-9a-z                     -      amp                     w       lt   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  TimeSpan FromMilliseconds 250                     catch  RegexMatchTimeoutException                      return false                       private string DomainMapper Match match                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

User · Answer

Check email string is right format or wrong format by System Text RegularExpressions       public static bool IsValidEmailId string InputEmail                Regex regex   new Regex       w   -       w -         w  2 3                 Match match   regex Match InputEmail           if  match Success              return true          else             return false             protected void Email TextChanged object sender  EventArgs e                String UserEmail   Email Text          if  IsValidEmailId UserEmail                         Label4 Text    This email is correct formate                     else                       Label4 Text    This email isn t correct formate

User · Answer

I use this single liner method which does the work for me-  using System ComponentModel DataAnnotations  public bool IsValidEmail string source        return new EmailAddressAttribute   IsValid source       Per the comments  this will  fail  if the source  the email address  is null   public static bool IsValidEmailAddress this string address    gt  address    null  amp  amp  new EmailAddressAttribute   IsValid address

User · Answer

Generally speaking  a regular expression to validate email addresses is not an easy thing to come up with  at the time of this writing  the syntax of an email address must follow a relatively high number of standards and implementing all of them within a regular expression is practically unfeasible   I highly suggest you to try our EmailVerify NET  a mature  NET library which can validate email addresses following all of the current IETF standards  RFC 1123  RFC 2821  RFC 2822  RFC 3696  RFC 4291  RFC 5321 and RFC 5322   tests the related DNS records  checks if the target mailboxes can accept messages and can even tell if a given address is disposable or not   Disclaimer  I am the lead developer for this component

User · Answer

I think the best way is as follow       public static bool EmailIsValid string email                string expression      w   -      w      w   -    w        w   -    w               if  Regex IsMatch email  expression                         if  Regex Replace email  expression  string Empty  Length    0                                return true                                  return false          You can have this static function in a general class

User · Answer

To be honest  in production code  the best I do is check for an   symbol   I m never in a place to be completely validating emails  You know how I see if it was really valid  If it got sent  If it didn t  it s bad  if it did  life s good  That s all I need to know

User · Answer

Simple way to identify the emailid is valid or not   public static bool EmailIsValid string email            return Regex IsMatch email        w-           0-9  1 3    0-9  1 3    0-9  1 3         w-          a-zA-Z  2 4   0-9  1 3

User · Answer

net 4 5 added  System ComponentModel DataAnnotations EmailAddressAttribute  You can browse the EmailAddressAttribute s source  this is the Regex it uses internally   const string pattern          a-z   d        amp       -                  u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF        a-z   d        amp       -                  u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF          x22      x20  x09    x0d x0a     x20  x09        x01- x08 x0b x0c x0e- x1f x7f   x21   x23- x5b    x5d- x7e    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF         x01- x09 x0b x0c x0d- x7f    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF          x20  x09    x0d x0a     x20  x09      x22        a-z   d   u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF      a-z   d   u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF    a-z   d -          u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF     a-z   d   u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF           a-z    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF      a-z    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF    a-z   d -          u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF     a-z    u00A0- uD7FF uF900- uFDCF uFDF0- uFFEF

User · Answer

Here s my answer -- Phil s solution fails for single letter domains like  someone q com    Believe it or not  that s used     goes to centurylink  for instance    Phil s answer is also going to work only with PCRE standard    so C  will take it  but javascript is going to bomb   It s too complex for javascript   So you can t use Phil s solution for mvc validation attributes   Here s my regex   It ll work nicely with MVC validation attributes  - Everything before the   is simplified  so that at least javascript will work  I m okay relaxing validation here as long as exchange server doesn t give me a 5 1 3  - Everything after the   is Phil s solution modified for single letter domains   public const string EmailPattern               s   w -           w -           A-Za-z0-9    w  -   A-Za-z0-9      A-Za-z  A-Za-z     A-Za-z       For people suggesting using system net mail MailMessage    that thing is WAY to flexible   Sure  C  will accept the email  but then exchange server will bomb with 5 1 3 runtime error as soon as you try to send the email

User · Answer

I just want to point out  that there has been a recent addition to the  NET documentation regarding email validation  also utilitzing Regex operations  A thorough explanation to their implementation can be found there  https   docs microsoft com en-us dotnet standard base-types how-to-verify-that-strings-are-in-valid-email-format For convenience  here is a list of their test results           Valid  david jones proseware com          Valid  d j server1 proseware com          Valid  jones ms1 proseware com          Invalid  j  server1 proseware com          Valid  j proseware com9          Valid  js internal proseware com          Valid  j 9  129 126 118 1           Invalid  j  s proseware com          Invalid  js  proseware com          Invalid  js proseware  com          Valid  js proseware com9          Valid  j s server1 proseware com          Valid   quot j  quot s  quot  quot  proseware com          Valid  js contoso

User · Answer

If you really and I mean really want to know if an email address is valid   ask the mail exchanger to prove it  no regex needed  I can provide the code if requested   General steps are as follows  1  does email address have a domain name part   index of     0  2  using a DNS query ask if domain has a mail exchanger 3  open tcp connection to mail exchanger 4  using the smtp protocol  open a message to the server using the email address as the reciever 5  parse the server s response  6  quit the message if you made it this far  everything is good   This is as you can imagine  very expensive time wise and relies on smtp  but it does work

User · Answer

This is an old question  but all the answers I ve found on SO  including more recent ones  are answered similarly to this one   However  in  Net 4 5   MVC 4 you can add email address validation to a form by adding the  EmailAddress  annotation from System ComponentModel DataAnnotations  so I was wondering why I couldn t just use the built-in functionality from  Net in general     This seems to work  and seems to me to be fairly elegant   using System ComponentModel DataAnnotations   class ValidateSomeEmails       static void Main string   args                var foo   new EmailAddressAttribute            bool bar          bar   foo IsValid  someone somewhere com              true         bar   foo IsValid  someone somewhere co uk            true         bar   foo IsValid  someone tag somewhere net          true         bar   foo IsValid  futureTLD somewhere fooo           true          bar   foo IsValid  fdsa                               false         bar   foo IsValid  fdsa                               false         bar   foo IsValid  fdsa fdsa                          false         bar   foo IsValid  fdsa fdsa                          false            one-liner         if  new EmailAddressAttribute   IsValid  someone somewhere com                bar   true

User · Answer

private static bool IsValidEmail string emailAddress        const string validEmailPattern                     r          r                                                     -a-z0-9     amp                   lt             lt                                                  a-z0-9   w  -   a-z0-9    a-z  a-z     a-z          return new Regex validEmailPattern  RegexOptions IgnoreCase  IsMatch emailAddress

User · Answer

I took Phil s answer from  1 and created this class  Call it like this  bool isValid   Validator EmailIsValid emailString    Here is the class   using System Text RegularExpressions   public static class Validator        static Regex ValidEmailRegex   CreateValidEmailRegex              lt summary gt          Taken from http   haacked com archive 2007 08 21 i-knew-how-to-validate-an-email-address-until-i aspx          lt  summary gt           lt returns gt  lt  returns gt      private static Regex CreateValidEmailRegex                 string validEmailPattern                     r          r                            -a-z0-9     amp                   lt             lt                         a-z0-9   w  -   a-z0-9    a-z  a-z     a-z              return new Regex validEmailPattern  RegexOptions IgnoreCase              internal static bool EmailIsValid string emailAddress                bool isValid   ValidEmailRegex IsMatch emailAddress            return isValid

User · Answer

The most voted answer from  Cogwheel is best answer however i have tried to implement trim   string method so it will trim all user white space from string start to end  Check the code bellow for full example-  bool IsValidEmail string email        try               email   email Trim            var addr   new System Net Mail MailAddress email           return addr Address    email            catch               return false

User · Answer

public bool IsValidEmail string email                try                       var addr   new System Net Mail MailAddress email               return addr Address    email                    catch                       return false

User · Answer

In case you are using FluentValidation you could write something as simple as this   public cass User       public string Email   get  set       public class UserValidator   AbstractValidator lt User gt        public UserValidator                 RuleFor x   gt  x Email  EmailAddress   WithMessage  The text entered is not a valid email address                 Validates an user   var validationResult   new UserValidator   Validate new User   Email    a  flkdj          This will return false  since the user email is not valid  bool userIsValid   validationResult IsValid

User · Answer

In a  try block  send a verification email  Make the user open the email and click a link verifying the email is real    Until this process completes successfully  the email is assumed to be invalid

User · Answer

The most elegant way is to use  Net s built in methods   These methods    Are tried and tested  These methods are used in my own professional projects  Use regular expressions internally  which are reliable and fast   Made by Microsoft for C   There s no need to reinvent the wheel  Return a bool result  True means the email is valid    For users of  Net 4 5 and greater  Add this Reference to your project      System ComponentModel DataAnnotations   Now you can use the following code    new EmailAddressAttribute   IsValid  youremailhere test test       Example of use  Here are some methods to declare   protected List lt string gt  GetRecipients      Gets recipients from TextBox named  TxtRecipients        List lt string gt  MethodResult   null       try               List lt string gt  Recipients   TxtRecipients Text Replace          Replace          Split      ToList             List lt string gt  RecipientsCleaned   new List lt string gt              foreach  string Recipient in RecipientsCleaned                        if   String IsNullOrWhiteSpace Recipient                                 RecipientsNoBlanks Add Recipient                                      MethodResult   RecipientsNoBlanks             catch   Exception ex                  ex HandleException               return MethodResult       public static bool IsValidEmailAddresses List lt string gt  recipients        List lt string gt  InvalidAddresses   GetInvalidEmailAddresses recipients        return InvalidAddresses    null  amp  amp  InvalidAddresses Count    0      public static List lt string gt  GetInvalidEmailAddresses List lt string gt  recipients        List lt string gt  MethodResult   null       try               List lt string gt  InvalidEmailAddresses   new List lt string gt              foreach  string Recipient in recipients                        if    new EmailAddressAttribute   IsValid Recipient    amp  amp   InvalidEmailAddresses Contains Recipient                                 InvalidEmailAddresses Add Recipient                                      MethodResult   InvalidEmailAddresses             catch   Exception ex                  ex HandleException                return MethodResult          and code demonstrating them in action   List lt string gt  Recipients   GetRecipients     bool IsValidEmailAddresses   IsValidEmailAddresses Recipients    if  IsValidEmailAddresses          Emails are valid  Your code here    else       StringBuilder sb   new StringBuilder         sb Append  The following addresses are invalid          List lt string gt  InvalidEmails   GetInvalidEmailAddresses Recipients        foreach  string InvalidEmail in InvalidEmails                sb Append   n    InvalidEmail               MessageBox Show sb ToString          In addition  this example    Extends beyond the spec since a single string is used to contain 0  one or many email addresses sperated by a semi-colon    Clearly demonstrates how to use the IsValid method of the EmailAddressAttribute object    Alternative  for users of a version of  Net less than 4 5  For situations where  Net 4 5 is not available  I use the following solution   Specifically  I use   public static bool IsValidEmailAddress string emailAddress        bool MethodResult   false       try               MailAddress m   new MailAddress emailAddress            MethodResult   m Address    emailAddress             catch    Exception ex                  ex HandleException                return MethodResult      public static List lt string gt  GetInvalidEmailAddresses List lt string gt  recipients        List lt string gt  MethodResult   null       try               List lt string gt  InvalidEmailAddresses   new List lt string gt              foreach  string Recipient in recipients                        if   IsValidEmail Recipient   amp  amp   InvalidEmailAddresses Contains Recipient                                 InvalidEmailAddresses Add Recipient                                      MethodResult   InvalidEmailAddresses             catch    Exception ex                  ex HandleException                return MethodResult

User · Answer

lt summary gt          Validates the email if it follows the valid email format          lt  summary gt           lt param name  emailAddress  gt  lt  param gt           lt returns gt  lt  returns gt      public static bool EmailIsValid string emailAddress                  if string is not null and empty then check for email follow the format         return string IsNullOrEmpty emailAddress  false   new Regex                   r          r          -a-z0-9     amp                   lt             lt       a-z0-9   w  -   a-z0-9    a-z  a-z     a-z     RegexOptions IgnoreCase  IsMatch emailAddress

User · Answer

Using the Internal Regex used in creating the  new EmailAddressAttribute     component in  Net4 5     using System ComponentModel DataAnnotations             To Validate an Email Address      Tested and Working   public bool IsEmail string email        if  String IsNullOrEmpty email           return false         try               Regex  regex   new Regex       a-z    d         amp          -                       u00A0-  uD7FF  uF900-  uFDCF  uFDF0-  uFFEF                              a-z    d         amp          -                       u00A0-  uD7FF  uF900-  uFDCF  uFDF0-  uFFEF           x22                            x20   x09     x0d  x0a      x20   x09         x01-  x08  x0b  x0c  x0e-  x1f  x7f    x21    x23-  x5b     x5d-  x7e                          u00A0-  uD7FF  uF900-  uFDCF  uFDF0-  uFFEF            x01-  x09  x0b  x0c  x0d-  x7f     u00A0-  uD7FF  uF900-  uFDCF  u                     FDF0-  uFFEF           x20   x09     x0d  x0a      x20   x09       x22        a-z    d    u00A0-  uD7FF  uF900-  uFDCF  uFDF0-  uFFEF                           a-z    d    u00A0-  uD7FF  uF900-  uFDCF  uFDF0-  uFFEF    a-z    d -            u00A0-  uD7FF  uF900-  uFDCF  uFDF0-  uFFEF     a-z    d                         u00A0-  uD7FF  uF900-  uFDCF  uFDF0-  uFFEF            a-z     u00A0-  uD7FF  uF900-  uFDCF  uFDF0-  uFFEF      a-z     u00A0-  uD7FF  uF900                     -  uFDCF  uFDF0-  uFFEF    a-z    d -            u00A0-  uD7FF  uF900-  uFDCF  uFDF0-  uFFEF     a-z     u00A0-  uD7FF  uF900-  uFDCF  uFDF0-  uFF                     EF            RegexOptions IgnoreCase   RegexOptions ExplicitCapture   RegexOptions Compiled           return  regex IsMatch email             catch  RegexMatchTimeoutException                return false            Also  You can use this   http   msdn microsoft com en-us library 01escwtf v vs 110  aspx

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Based on the answer of  Cogwheel i want to share a modified solution that works for SSIS and the  Script Component     Place the  Script Component  into your Data Flow connect and then open it  In the section  Input Columns  set the field that contains the E-Mail Adresses to  ReadWrite   in the example  fieldName    Switch back to the section  Script  and click on  Edit Script   Then you need to wait after the code opens  Place this code in the right method   public override void Input0 ProcessInputRow Input0Buffer Row        string email   Row fieldName       try               System Net Mail MailAddress addr   new System Net Mail MailAddress email           Row fieldName  addr Address ToString              catch               Row fieldName    WRONGADDRESS              Then you can use a Conditional Split to filter out all invalid records or whatever you want to do

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For the simple email like goerge xxx com  below code is sufficient     public static bool ValidateEmail string email                        System Text RegularExpressions Regex emailRegex   new System Text RegularExpressions Regex       w   -       w -         w  2 3                     System Text RegularExpressions Match emailMatch   emailRegex Match email               return emailMatch Success

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Personally  I would say that you should just make sure there is an   symbol in there  with possibly a   character   There s many regexes you could use of varying correctness  but I think most of these leave out valid email addresses  or let invalid ones through   If people want to put in a fake email address  they will put in a fake one   If you need to verify that the email address is legit  and that the person is in control of that email address  then you will need to send them an email with a special coded link so they can verify that it indeed is a real address

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I ended up using this regex  as it successfully validates commas  comments  Unicode characters and IP v4  domain addresses  Valid addresses will be    quot   quot  example org  comment test example org      example org       example org test  192 168 1 1    public const string REGEX EMAIL     quot         w     amp               -         lt  gt             s   quot  quot         lt  gt             s   quot  quot          quot  quot     quot  quot        w     amp               -            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      quot

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This may be the best way for the email validation for your textbox   string pattern   null  pattern       0-9a-zA-Z   -     w   0-9a-zA-Z      0-9a-zA-Z  -  w   0-9a-zA-Z       a-zA-Z  2 9       if  Regex IsMatch  txtemail Text   pattern     MessageBox Show   Valid Email address       else   MessageBox Show  Invalid Email Email        Just include in any function where you want

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What about this  bool IsValidEmail string email        try           var addr   new System Net Mail MailAddress email           return addr Address    email            catch           return false           Per Stuart s comment  this compares the final address with the original string instead of always returning true  MailAddress tries to parse a string with spaces into  quot Display Name quot  and  quot Address quot  portions  so the original version was returning false positives   To clarify  the question is asking whether a particular string is a valid representation of an e-mail address  not whether an e-mail address is a valid destination to send a message  For that  the only real way is to send a message to confirm  Note that e-mail addresses are more forgiving than you might first assume  These are all perfectly valid forms   cog wheel  quot cogwheel the orange quot  example com 123   xyz  For most use cases  a false  quot invalid quot  is much worse for your users and future proofing than a false  quot valid quot   Here s an article that used to be the accepted answer to this question  that answer has since been deleted   It has a lot more detail and some other ideas of how to solve the problem  Providing sanity checks is still a good idea for user experience  Assuming the e-mail address is valid  you could look for known top-level domains  check the domain for an MX record  check for spelling errors from common domain names  gmail cmo   etc  Then present a warning giving the user a chance to say  quot yes  my mail server really does allow  as an email address  quot   As for using exception handling for business logic  I agree that is a thing to be avoided  But this is one of those cases where the convenience and clarity may outweigh the dogma  Besides  if you do anything else with the e-mail address  it s probably going to involve turning it to a MailAddress  Even if you don t use this exact function  you will probably want to use the same pattern  You can also check for specific kinds of failure by catching different exceptions  null  empty  or invalid format   --- Further reading --- Documentation for System Net Mail MailAddress Explanation of what makes up a valid email address

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What if you combine multiple solutions to make a perfect code   i got top 2 Solutions having highest Ranks and Reviews and combined them to get more accurate Answers  its Short  fast and adorable       public static bool isValidEmail string email                try                       var addr   new System Net Mail MailAddress email               if  addr Address    email                                string expression      w   -      w      w   -    w        w   -    w                       if  Regex IsMatch email  expression                                         if  Regex Replace email  expression  string Empty  Length    0                           return true                                     return false                            return false                     catch                       return false

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a little modification to  Cogwheel answer  public static bool IsValidEmail this string email         skip the exception  amp  return early if possible   if  email IndexOf       lt   0  return false     try         var address   new MailAddress email       return address Address    email        catch         return false

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As mentioned in many answers  the domain of email addresses is complex  I would strongly discourage the use of a regex in this case  Those who match  most  cases are extremely complex to read and therefor to maintain  Furthermore  the still have difficulties supporting all cases  and are slow   Microsoft s EmailAddress class helps a bit in that respect  but is not perfect either  I would argue  For an open source project I gave it try some years ago  by using a customized EmailParser   That is used in  EmailAddress https   github com Qowaiv Qowaiv blob master src Qowaiv EmailAddress cs    By using this approach  you re not only to validate email addresses  but also by cleaning out multiple formats of display names  getting rid of the mailto -prefix  and normalizing domain literals based on IP-addresses  and lowercasing everything  note that the local part officially is case sensitive    Scenario s your solution should support  and the mentioned one does     TestCase null    TestCase       TestCase     test com     TestCase   a test com     TestCase  ab sd dd     TestCase    s dd     TestCase  ab 988 120 150 10     TestCase  ab 120 256 256 120     TestCase  ab 120 25 1111 120     TestCase  ab  188 120 150 10     TestCase  ab 188 120 150 10      TestCase  ab  188 120 150 10  com     TestCase  a b -de cc     TestCase  a bde- cc     TestCase  a bde c-c     TestCase  a bde cc      TestCase  ab b de cc     TestCase  a  b bde cc     TestCase    bde cc      TestCase  plainaddress     TestCase  plain address     TestCase              com     TestCase   domain com     TestCase  Joe Smith  amp lt email domain com amp gt      TestCase  email domain com     TestCase  email domain domain com     TestCase   email domain com     TestCase  email  domain com     TestCase  email  email domain com     TestCase  email -domain com     TestCase  email domain- com     TestCase  email domain com-     TestCase  email  domain com     TestCase  email domain com      TestCase  email domain  com     TestCase  email 111 222 333     TestCase  email 111 222 333 256     TestCase  email  123 123 123 123     TestCase  email  123 123 123  123     TestCase  email 123 123 123 123      TestCase  email 123 123  123 123      TestCase  email  leftbracket com     TestCase  email rightbracket  com     TestCase  email p pe com     TestCase  isis 100  nl     TestCase  email dollar  com     TestCase  email r amp amp d com     TestCase  email  hash com     TestCase  email wave tilde com     TestCase  email exclamation mark com     TestCase  email question mark com     TestCase  email obelix asterisk com     TestCase  email grave accent com     TestCase  email colon colon com     TestCase  email caret xor com     TestCase  email  qowaiv com     TestCase  email plus  com     TestCase  email domain com gt      TestCase  email   nested    plus com     TestCase  email mirror  plus com     TestCase  email plus com  not closed comment     TestCase  email with   in comment plus com     TestCase     Joe Smith email domain com     TestCase     Joe Smith  email domain com     TestCase     Joe Smith  email domain com     TestCase  email mailto domain com     TestCase  mailto mailto email domain com     TestCase  Display Name  lt email plus com gt   after name with display      TestCase  ReDoSaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa    public void IsInvalid string email        Assert IsFalse EmailAddress IsValid email   email       TestCase  w com     TestCase  w b f test com     TestCase  w b f test museum     TestCase  a a test com     TestCase  ab 288 120 150 10 com     TestCase  ab 188 120 150 10     TestCase  ab 1 0 0 10     TestCase  ab 120 25 254 120     TestCase  ab 01 120 150 1     TestCase  ab 88 120 150 021     TestCase  ab 88 120 150 01     TestCase  ab  120 254 254 120      TestCase  local 2001 0db8 85a3 0000 0000 8a2e 0370 7334     TestCase  local  2001 0db8 85a3 0000 0000 8a2e 0370 7334      TestCase  2 bde cc     TestCase  - bde cc     TestCase  a2 bde cc     TestCase  a-b bde cc     TestCase  ab b-de cc     TestCase  a b bde cc     TestCase  f f f bde cc     TestCase  ab c bde cc     TestCase   -  bde cc     TestCase  k haak 12move nl     TestCase  K HAAK 12MOVE NL     TestCase  email domain com     TestCase  email domain     TestCase        domain com     TestCase  local       com     TestCase  firstname lastname domain com     TestCase  email subdomain domain com     TestCase  firstname lastname domain com     TestCase  email 123 123 123 123     TestCase  email  123 123 123 123      TestCase  1234567890 domain com     TestCase  a domain com     TestCase  a b c d domain com     TestCase  aap 123 noot mies domain com     TestCase  1 domain com     TestCase  email domain-one com     TestCase          domain com     TestCase  email domain topleveldomain     TestCase  email domain co jp     TestCase  firstname-lastname domain com     TestCase  firstname-lastname d com     TestCase  FIRSTNAME-LASTNAME d--n com     TestCase  first-name-last-name d-a-n com     TestCase   local name  with  leftbracket com     TestCase   local name  with  rightbracket com     TestCase   local  name with  pipe com     TestCase   local  name with  percentage com     TestCase   local  name with  dollar com     TestCase   amp local amp  amp name amp with amp   amp com     TestCase   local  name with  hash com     TestCase   local  name with  tilde com     TestCase   local  name with  exclamation com     TestCase   local  name with  question com     TestCase   local  name with  asterisk com     TestCase   local  name with  grave-accent com     TestCase   local  name with  xor com     TestCase   local  name with  equality com     TestCase   local  name with  equality com     TestCase  Joe Smith  lt email domain com gt      TestCase  email domain com  joe Smith      TestCase     Joe Smith   email domain com     TestCase     Joe  tSmith   email domain com     TestCase     Joe   Smith   email domain com     TestCase   Test   lt gaaf  lt email domain com gt      TestCase  MailTo casesensitve domain com     TestCase  mailto email domain com     TestCase  Joe Smith  lt mailto email domain com gt      TestCase  Joe Smith  lt mailto email with comment  domain com gt      TestCase     With extra  lt  within quotes   Display Name lt email domain com gt      TestCase  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa    public void IsValid string email        Assert IsTrue EmailAddress IsValid email   email

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Some time back  I wrote an EmailAddressValidationAttribute that should properly validate pretty much any relatively normal email address of the form  local-part domain   It s a System ComponentModel DataAnnotations ValidationAttribute  so usage is really simple   And  since digging through all the RFCs and errata and assembling all the bits required to properly enumerate all the rules is   tedious  mdash  at best   mdash  I posted the source code for the validator in my answer to the question C  Email Address validation for the source code   My validator isn t perfect by any stretch of the imagination  though Just for starters  it doesn t have any built-in support for emitting client-side javascript validation  though it wouldn t be too difficult to add that in  From my answer above      Here s the validation attribute I wrote  It validates pretty much every  raw  email   address  that is those of the form local-part domain  It doesn t support any of   the other  more   creative constructs that the RFCs allow  this list is not   comprehensive by any means           comments  e g   jsmith whizbang com  work     quoted strings  escaped text  to allow characters not allowed in an atom    domain literals  e g  foo  123 45 67 012     bang-paths  aka source routing    angle addresses  e g  John Smith  lt jsmith whizbang com gt     folding whitespace   double-byte characters in either local-part or domain  7-bit ASCII only     etc          It should accept almost any email address that can be expressed thusly         foo bar bazbat com         without requiring the use of quotes      angle brackets    lt       or square brackets            No attempt is made to validate that the rightmost dns label in the domain is a valid   TLD  top-level domain   That is because the list of TLDs is far larger now than the    big 6    com   edu   gov   mil   net   org  plus 2-letter ISO country codes    ICANN actually updates the TLD list daily  though I suspect that the list   doesn t actually change daily  Further   ICANN just approved a big expansion of the   generic TLD namespace  2    And some email addresses don t have what you d recognize   as a TLD  did you know that postmaster   is theoretically valid and mailable  Mail   to that address should get delivered to the postmaster of the DNS root zone        Extending the regular expression to support domain literals shouldn t be too difficult

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There are a lot of strong answers here  However  I recommend that we take a step back   Cogwheel answers the question https   stackoverflow com a 1374644 388267  Nevertheless  it could be costly in a bulk validation scenario  if many of the email address being validated are invalid  I suggest that we employ a bit of logic before we enter into his try-catch block  I know that the following code could be written using RegEx but that could be costly for new developers to understand  This is my twopence worth       public static bool IsEmail this string input                if  string IsNullOrWhiteSpace input   return false              MUST CONTAIN ONE AND ONLY ONE           var atCount   input Count c   gt  c                  if  atCount    1  return false              MUST CONTAIN PERIOD         if   input Contains       return false                MUST OCCUR BEFORE LAST PERIOD         var indexOfAt   input IndexOf      StringComparison Ordinal           var lastIndexOfPeriod   input LastIndexOf      StringComparison Ordinal           var atBeforeLastPeriod   lastIndexOfPeriod  gt  indexOfAt          if   atBeforeLastPeriod  return false              CODE FROM COGWHEEL S ANSWER  https   stackoverflow com a 1374644 388267          try                       var addr   new System Net Mail MailAddress input               return addr Address    input                    catch                       return false

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Email address validation is not as easy as it might seem  It s actually theoretically impossible to fully validate an email address using just a regular expression   Check out my blog post about it for a discussion on the subject and a F  implementation using FParsec    shameless plug

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I use this one to validate emails often and it works like a charm  This validates that the email must have atleast one character before the    and at least one character before the      public static bool ValidateEmail string value  bool required  int minLength  int maxLength                       value   value Trim               if  required    false  amp  amp  value        return true             if  required  amp  amp  value        return false             if  value Length  lt  minLength    value Length  gt  maxLength  return false                Email must have at least one character before an    and at least one character before the              int index   value IndexOf                  if  index  lt  1    value LastIndexOf       lt  index   2  return false             return true

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Short and accurate code    string Email   txtEmail Text  if  Email IsValidEmail           use code here     public static bool IsValidEmail this string email      string pattern                     r          r                -a-z0-9     amp                   lt             lt             a-z0-9   w  -   a-z0-9    a-z  a-z     a-z           var regex   new Regex pattern  RegexOptions IgnoreCase         return regex IsMatch email

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public static bool IsEmail string strEmail        Regex rgxEmail   new Regex      a-zA-Z0-9  -           0-9  1 3                                         0-9  1 3    0-9  1 3        a-zA-Z0-9 -                                               a-zA-Z  2 4   0-9  1 3                return rgxEmail IsMatch strEmail

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Another Regex Match answer            lt summary gt         Validates the email input         lt  summary gt     internal static bool ValidateEmail string  emailAddress                 string  regexPattern          w-        w-     a-zA-Z  1    w-  2                               0-1   0-9  1 2  25 0-5  2 0-4  0-9      0-1   0-9  1 2  25 0-5  2 0-4  0-9                            0-1   0-9  1 2  25 0-5  2 0-4  0-9      0-1   0-9  1 2  25 0-5  2 0-4  0-9    1                          a-zA-Z    w-       a-zA-Z  2 4               return  string IsNullOrEmpty  emailAddress     false  amp  amp  System Text RegularExpressions Regex IsMatch  emailAddress   regexPattern                 true               false

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