验证字符串是否是有效的电子邮件地址的最优雅的代码是什么?
当前回答
我经常用这个来验证电子邮件，它就像一个魅力。这验证了电子邮件必须在@之前至少有一个字符，并且在“”之前至少有一个字符。
public static bool ValidateEmail(string value, bool required, int minLength, int maxLength)
{
value = value.Trim();
if (required == false && value == "") return true;
if (required && value == "") return false;
if (value.Length < minLength || value.Length > 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 < 1 || value.LastIndexOf('.') < index + 2) return false;
return true;
}
其他回答
.net 4.5增加了System.ComponentModel.DataAnnotations.EmailAddressAttribute
你可以浏览EmailAddressAttribute的源代码，这是它内部使用的正则表达式:
const string pattern = @"^((([a-z]|\d|[!#\$%&'\*\+\-\/=\?\^_`{\|}~]|[\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF])+(\.([a-z]|\d|[!#\$%&'\*\+\-\/=\?\^_`{\|}~]|[\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])))\.?$";
我是来偷电子邮件的验证码的。然后我发现答案中的代码不必要地扩展了。我相信我用最短的方式写出了最好的解决方案:
public static bool IsEmail(string email)
{
try
{
return new System.Net.Mail.MailAddress(email).Address == email && !email.Trim().EndsWith(".");
}
catch
{
return false;
}
}
我根据维基百科的规则和样本地址创建了一个电子邮件地址验证程序。对于那些不介意多看一点代码的人，这里。说实话，我不知道电子邮件地址规范中有这么多疯狂的规则。我没有完全验证主机名或ipaddress，但它仍然通过了维基百科上的所有测试用例。
using Microsoft.VisualStudio.TestTools.UnitTesting;
namespace EmailValidateUnitTests
{
[TestClass]
public class EmailValidationUnitTests
{
[TestMethod]
public void TestEmailValidate()
{
// Positive Assertions
Assert.IsTrue("prettyandsimple@example.com".IsValidEmailAddress());
Assert.IsTrue("very.common@example.com".IsValidEmailAddress());
Assert.IsTrue("disposable.style.email.with+symbol@example.com".IsValidEmailAddress());
Assert.IsTrue("other.email-with-dash@example.com".IsValidEmailAddress());
Assert.IsTrue("\"much.more unusual\"@example.com".IsValidEmailAddress());
Assert.IsTrue("\"very.unusual.@.unusual.com\"@example.com".IsValidEmailAddress()); //"very.unusual.@.unusual.com"@example.com
Assert.IsTrue("\"very.(),:;<>[]\\\".VERY.\\\"very@\\\\ \\\"very\\\".unusual\"@strange.example.com".IsValidEmailAddress()); //"very.(),:;<>[]\".VERY.\"very@\\ \"very\".unusual"@strange.example.com
Assert.IsTrue("admin@mailserver1".IsValidEmailAddress());
Assert.IsTrue("#!$%&'*+-/=?^_`{}|~@example.org".IsValidEmailAddress());
Assert.IsTrue("\"()<>[]:,;@\\\\\\\"!#$%&'*+-/=?^_`{}| ~.a\"@example.org".IsValidEmailAddress()); //"()<>[]:,;@\\\"!#$%&'*+-/=?^_`{}| ~.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<h>i[j\\k]l@example.com".IsValidEmailAddress()); //a"b(c)d,e:f;g<h>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!#$%&'*+-/=?^_`{|}~";
private const string ValidQuotedLocalPartChars = "(),:;<>@[]. ";
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 < 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) >= 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 && ((commentEnd + 1) < s.Length) && 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) >= 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) >= 0 || ValidQuotedLocalPartChars.IndexOf(c) >= 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) >= 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 && (commentStart > 0) && s[commentStart - 1] != '@') { valid = false; break; }
}
}
else if (mode == EmailParseMode.DomainSplit)
{
if (ValidDomainPartChars.IndexOf(c) >= 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) >= 0) { hasDomain = true; }
else { valid = false; break; }
}
else if (mode == EmailParseMode.BracketedDomain)
{
if (c == ']') { mode = EmailParseMode.BracketedDomainEnd; }
else if (c == '.' || ValidDomainPartChars.IndexOf(c) >= 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 && commentStart >= 0);
return hasLocal && hasDomain && valid && !unfinishedComment;
}
}
}
在c#的regex中有文化问题，而不是js。所以我们需要在US模式下使用regex进行邮件检查。如果你不使用ECMAScript模式，你的语言特殊字符是在A-Z与正则表达式中隐含的。
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)
这是一个老问题，但我在SO上找到的所有答案，包括最近的答案，都与这个问题类似。然而，在。net 4.5 / MVC 4中，你可以通过从System.ComponentModel中添加[EmailAddress]注释来向表单添加电子邮件地址验证。DataAnnotations，所以我想知道为什么我不能只使用。net的内置功能。
这似乎是可行的，而且在我看来是相当优雅的:
using System.ComponentModel.DataAnnotations;
class ValidateSomeEmails
{
static void Main(string[] args)
{
var email = new EmailAddressAttribute();
email.IsValid("someone@somewhere.com"); //true
email.IsValid("someone@somewhere.co.uk"); //true
email.IsValid("someone+tag@somewhere.net"); //true
email.IsValid("futureTLD@somewhere.fooo"); //true
email.IsValid("fdsa"); //false
email.IsValid("fdsa@"); //false
email.IsValid("fdsa@fdsa"); //false
email.IsValid("fdsa@fdsa."); //false
//one-liner
if (new EmailAddressAttribute().IsValid("someone@somewhere.com"))
return true;
}
}
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