以下代码是基于微软在github上的数据注释实现的，我认为这是对电子邮件最完整的验证:

public static Regex EmailValidation()
{
    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])))\.?$";
    const RegexOptions options = RegexOptions.Compiled | RegexOptions.IgnoreCase | RegexOptions.ExplicitCapture;

    // Set explicit regex match timeout, sufficient enough for email parsing
    // Unless the global REGEX_DEFAULT_MATCH_TIMEOUT is already set
    TimeSpan matchTimeout = TimeSpan.FromSeconds(2);

    try
    {
        if (AppDomain.CurrentDomain.GetData("REGEX_DEFAULT_MATCH_TIMEOUT") == null)
        {
            return new Regex(pattern, options, matchTimeout);
        }
    }
    catch
    {
        // Fallback on error
    }

    // Legacy fallback (without explicit match timeout)
    return new Regex(pattern, options);
}

我想@”^ ((\ w \.\-]+)@([\ w \-]+)((\.(\ w){2,3}) +)美元“应该工作。 你需要这样写

string email = txtemail.Text;
Regex regex = new Regex(@"^([\w\.\-]+)@([\w\-]+)((\.(\w){2,3})+)$");
Match match = regex.Match(email);
if (match.Success)
    Response.Write(email + " is correct");
else
    Response.Write(email + " is incorrect");

请注意，如果出现以下情况，此操作将失败:

符号@后面有一个子域。 您使用的TLD长度大于3，例如.info

以下是我从这里收集信息和微软文档后的解决方案:

/// <summary>
/// * TLD support from 2 to 5 chars (modify the values as you want)
/// * Supports: abc@gmail.com.us
/// * Non-sensitive case 
/// * Stops operation if takes longer than 250ms and throw a detailed exception
/// </summary>
/// <param name="email"></param>
/// <returns>valid: true | invalid: false </returns>
/// <exception cref="ArgumentException"></exception>

private bool validateEmailPattern(string email) {
    try {
        return Regex.IsMatch(email,
            @"^([\w\.\-]+)@([\w\-]+)((\.(\w){2,5})+)$",
            RegexOptions.None, TimeSpan.FromMilliseconds(250));
    } catch (RegexMatchTimeoutException) {
        // throw an exception explaining the task was failed 
        _ = email ?? throw new ArgumentException("email, Timeout/failed regexr processing.", nameof(email));
    }
}

没有完美的正则表达式，但我认为，基于对RFC5322的研究，这个正则表达式相当强大。用c#字符串插值，我认为也很容易理解。

const string atext = @"a-zA-Z\d!#\$%&'\*\+-/=\?\^_`\{\|\}~";
var localPart = $"[{atext}]+(\\.[{atext}]+)*";
var domain = $"[{atext}]+(\\.[{atext}]+)*";
Assert.That(() => EmailRegex = new Regex($"^{localPart}@{domain}$", Compiled), 
Throws.Nothing);

用NUnit 2.x检查。

它采取了许多尝试，以创建一个电子邮件验证器，捕捉几乎所有的全球电子邮件需求。

扩展方法，你可以调用:

myEmailString.IsValidEmailAddress();

正则表达式模式字符串，你可以通过调用:

var myPattern = Regex.EmailPattern;

准则(主要是评论):

    /// <summary>
    /// Validates the string is an Email Address...
    /// </summary>
    /// <param name="emailAddress"></param>
    /// <returns>bool</returns>
    public static bool IsValidEmailAddress(this string emailAddress)
    {
        var valid = true;
        var isnotblank = false;

        var email = emailAddress.Trim();
        if (email.Length > 0)
        {
            // Email Address Cannot start with period.
            // Name portion must be at least one character
            // In the Name, valid characters are:  a-z 0-9 ! # _ % & ' " = ` { } ~ - + * ? ^ | / $
            // Cannot have period immediately before @ sign.
            // Cannot have two @ symbols
            // In the domain, valid characters are: a-z 0-9 - .
            // Domain cannot start with a period or dash
            // Domain name must be 2 characters.. not more than 256 characters
            // Domain cannot end with a period or dash.
            // Domain must contain a period
            isnotblank = true;
            valid = Regex.IsMatch(email, Regex.EmailPattern, RegexOptions.IgnoreCase) &&
                !email.StartsWith("-") &&
                !email.StartsWith(".") &&
                !email.EndsWith(".") && 
                !email.Contains("..") &&
                !email.Contains(".@") &&
                !email.Contains("@.");
        }

        return (valid && isnotblank);
    }

    /// <summary>
    /// Validates the string is an Email Address or a delimited string of email addresses...
    /// </summary>
    /// <param name="emailAddress"></param>
    /// <returns>bool</returns>
    public static bool IsValidEmailAddressDelimitedList(this string emailAddress, char delimiter = ';')
    {
        var valid = true;
        var isnotblank = false;

        string[] emails = emailAddress.Split(delimiter);

        foreach (string e in emails)
        {
            var email = e.Trim();
            if (email.Length > 0 && valid) // if valid == false, no reason to continue checking
            {
                isnotblank = true;
                if (!email.IsValidEmailAddress())
                {
                    valid = false;
                }
            }
        }
        return (valid && isnotblank);
    }

    public class Regex
    {
        /// <summary>
        /// Set of Unicode Characters currently supported in the application for email, etc.
        /// </summary>
        public static readonly string UnicodeCharacters = "À-ÿ\p{L}\p{M}ÀàÂâÆæÇçÈèÉéÊêËëÎîÏïÔôŒœÙùÛûÜü«»€₣äÄöÖüÜß"; // German and French

        /// <summary>
        /// Set of Symbol Characters currently supported in the application for email, etc.
        /// Needed if a client side validator is being used.
        /// Not needed if validation is done server side.
        /// The difference is due to subtle differences in Regex engines.
        /// </summary>
        public static readonly string SymbolCharacters = @"!#%&'""=`{}~\.\-\+\*\?\^\|\/\$";

        /// <summary>
        /// Regular Expression string pattern used to match an email address.
        /// The following characters will be supported anywhere in the email address:
        /// ÀàÂâÆæÇçÈèÉéÊêËëÎîÏïÔôŒœÙùÛûÜü«»€₣äÄöÖüÜß[a - z][A - Z][0 - 9] _
        /// The following symbols will be supported in the first part of the email address(before the @ symbol):
        /// !#%&'"=`{}~.-+*?^|\/$
        /// Emails cannot start or end with periods,dashes or @.
        /// Emails cannot have two @ symbols.
        /// Emails must have an @ symbol followed later by a period.
        /// Emails cannot have a period before or after the @ symbol.
        /// </summary>
        public static readonly string EmailPattern = String.Format(
            @"^([\w{0}{2}])+@{1}[\w{0}]+([-.][\w{0}]+)*\.[\w{0}]+([-.][\w{0}]+)*$",                     //  @"^[{0}\w]+([-+.'][{0}\w]+)*@[{0}\w]+([-.][{0}\w]+)*\.[{0}\w]+([-.][{0}\w]+)*$",
            UnicodeCharacters,
            "{1}",
            SymbolCharacters
        );
    }

目前对我来说，最好的方法是使用FluentValidation库。它有一个内置的电子邮件地址验证器。用法非常简单，你不必考虑正则表达式。

using FluentValidation;
public class TestClass
{
   public string Email { get; set; }
}

public class TestClassValidator: AbstractValidator<TestClass>
{
   public TestClassValidator()
   {            
      RuleFor(x => x.Email).EmailAddress().WithMessage($"nameof{(TestClass.Email)} is not a valid email address");
   }
}

我知道这个问题很久以前就被问过了，但也许用一种新的方法来刷新答案会对某人有所帮助。