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;
}
}
其他回答
这是你问题的答案，供你核对。
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, @"^(?("")("".+?(?<!\\)""@)|(([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]))$", RegexOptions.IgnoreCase, TimeSpan.FromMilliseconds(250));
}
catch (RegexMatchTimeoutException)
{
return false;
}
}
private string DomainMapper(Match match)
{
// IdnMapping class with default property values.
IdnMapping idn = new IdnMapping();
string domainName = match.Groups[2].Value;
try
{
domainName = idn.GetAscii(domainName);
}
catch (ArgumentException)
{
invalid = true;
}
return match.Groups[1].Value + domainName;
}
}
我根据维基百科的规则和样本地址创建了一个电子邮件地址验证程序。对于那些不介意多看一点代码的人，这里。说实话，我不知道电子邮件地址规范中有这么多疯狂的规则。我没有完全验证主机名或ipaddress，但它仍然通过了维基百科上的所有测试用例。
using Microsoft.VisualStudio.TestTools.UnitTesting;
namespace EmailValidateUnitTests
{
[TestClass]
public class EmailValidationUnitTests
{
[TestMethod]
public void TestEmailValidate()
{
// Positive Assertions
Assert.IsTrue("prettyandsimple@example.com".IsValidEmailAddress());
Assert.IsTrue("very.common@example.com".IsValidEmailAddress());
Assert.IsTrue("disposable.style.email.with+symbol@example.com".IsValidEmailAddress());
Assert.IsTrue("other.email-with-dash@example.com".IsValidEmailAddress());
Assert.IsTrue("\"much.more unusual\"@example.com".IsValidEmailAddress());
Assert.IsTrue("\"very.unusual.@.unusual.com\"@example.com".IsValidEmailAddress()); //"very.unusual.@.unusual.com"@example.com
Assert.IsTrue("\"very.(),:;<>[]\\\".VERY.\\\"very@\\\\ \\\"very\\\".unusual\"@strange.example.com".IsValidEmailAddress()); //"very.(),:;<>[]\".VERY.\"very@\\ \"very\".unusual"@strange.example.com
Assert.IsTrue("admin@mailserver1".IsValidEmailAddress());
Assert.IsTrue("#!$%&'*+-/=?^_`{}|~@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;
}
}
}
我总结了以上所有的答案，截至2021年，我在这门课上为自己写的答案:
public static class StringExt {
private const string emailPattern = @"^(?!\.)(""([^""\r\\]|\\[""\r\\])*""|"
+ @"([-a-z0-9!#$%&'*+/=?^_`{|}~]|(?<!\.)\.)*)(?<!\.)"
+ @"@[a-z0-9][\w\.-]*[a-z0-9]\.[a-z][a-z\.]*[a-z]$";
public static bool IsValidMailAddress(this string pThis)
=> pThis is not null
&& Regex.IsMatch(pThis, emailPattern, RegexOptions.IgnoreCase);
}
电子邮件地址验证并不像看起来那么简单。实际上，从理论上讲，仅使用正则表达式完全验证电子邮件地址是不可能的。
请查看我的博客文章，了解关于这个主题的讨论以及使用FParsec的f#实现。[/ shameless_plug]
我写了一个函数来检查电子邮件是否有效。在大多数情况下，这似乎对我很有效。
结果:
dasddas-@.com => FALSE
-asd@das.com => FALSE
as3d@dac.coas- => FALSE
dsq!a?@das.com => FALSE
_dasd@sd.com => FALSE
dad@sds => FALSE
asd-@asd.com => FALSE
dasd_-@jdas.com => FALSE
asd@dasd@asd.cm => FALSE
da23@das..com => FALSE
_dasd_das_@9.com => FALSE
d23d@da9.co9 => TRUE
dasd.dadas@dasd.com => TRUE
dda_das@das-dasd.com => TRUE
dasd-dasd@das.com.das => TRUE
代码:
private bool IsValidEmail(string email)
{
bool valid = false;
try
{
var addr = new System.Net.Mail.MailAddress(email);
valid = true;
}
catch
{
valid = false;
goto End_Func;
}
valid = false;
int pos_at = email.IndexOf('@');
char checker = Convert.ToChar(email.Substring(pos_at + 1, 1));
var chars = "qwertyuiopasdfghjklzxcvbnm0123456789";
foreach (char chr in chars)
{
if (checker == chr)
{
valid = true;
break;
}
}
if (valid == false)
{
goto End_Func;
}
int pos_dot = email.IndexOf('.', pos_at + 1);
if(pos_dot == -1)
{
valid = false;
goto End_Func;
}
valid = false;
try
{
checker = Convert.ToChar(email.Substring(pos_dot + 1, 1));
foreach (char chr in chars)
{
if (checker == chr)
{
valid = true;
break;
}
}
}
catch
{
valid = false;
goto End_Func;
}
Regex valid_checker = new Regex(@"^[a-zA-Z0-9_@.-]*$");
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;
}
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