Best Regular Expression for Email Validation in C

Question

I have seen a multitude of regular expressions for different programming languages that all purport to validate email addresses   I have seen many comments saying that the expressions in question do not work for certain cases and that they are either too strict or too permissive   What I m looking for is a regular expression that I can use in my C  code that is definitive   The best thing I have found is this      w   -       w -         w  2 3        Is there something better

User · Answer

Email Validation Regex    a-z0-9  -a-z0-9       -a-z0-9      a-z  2 5     Or    a-z0-9  -a-z0-9       -a-z0-9        a-z  2 5     Demo Link   https   regex101 com r kN4nJ0 53

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First option  bad because of throw-catch  but MS will do work for you    bool IsValidEmail string email        try           var mail   new System Net Mail MailAddress email           return true            catch           return false            Second option is read I Knew How To Validate An Email Address Until I Read The RFC and RFC specification

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I would like to suggest new EmailAddressAttribute   IsValid emailTxt  for additional validation before after validating using RegEx  Remember EmailAddressAttribute is part of System ComponentModel DataAnnotations namespace

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This C  function uses a regular expression to evaluate whether the passed email address is syntactically valid or not   public static bool isValidEmail string inputEmail       string strRegex        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              Regex re   new Regex strRegex      if  re IsMatch inputEmail       return  true      else     return  false

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Email address  RFC 2822 Format    Matches a normal email address     Does not check the top-level domain  Requires the  case insensitive    option to be ON     a-z0-9     amp              -        a-z0-9     amp              -         a-z0-9     a-z0-9-   a-z0-9        a-z0-9     a-z0-9-   a-z0-9      Usage     bool isEmail   Regex IsMatch emailString     A    a-z0-9     amp              -        a-z0-9     amp              -         a-z0-9     a-z0-9-   a-z0-9        a-z0-9     a-z0-9-   a-z0-9     Z   RegexOptions IgnoreCase

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Updated answer for 2019   Regex object is thread-safe for Matching functions  Knowing that and there are some performance options or cultural   language issues  I propose this simple solution   public static Regex  regex   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               RegexOptions CultureInvariant   RegexOptions Singleline    public static bool IsValidEmailFormat string emailInput        return  regex IsMatch emailInput       Alternative Configuration for Regex   public static Regex  regex   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               RegexOptions CultureInvariant   RegexOptions Compiled     I find that compiled is only faster on big string matches  like book parsing for example  Simple email matching is faster just letting Regex interpret   Thread Safety And Regex Regex Best Practices

[c#] Best Regular Expression for Email Validation in C#

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