为什么不使用基于EF6属性的电子邮件验证?

正如您在上面所看到的，电子邮件的Regex验证总是有一些漏洞。如果您使用的是EF6数据注释，则可以通过EmailAddress数据注释属性轻松实现可靠且更强的电子邮件验证。当我在电子邮件输入字段上获得移动设备特定的正则表达式失败时，我不得不删除以前用于电子邮件的正则表达式验证。当数据注释属性用于电子邮件验证时，移动设备上的问题就解决了。

public class LoginViewModel
{
    [EmailAddress(ErrorMessage = "The email format is not valid")]
    public string Email{ get; set; }

public static bool ValidateEmail(string str)
{                       
     return Regex.IsMatch(str, @"\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*");
}

我使用上面的代码来验证电子邮件地址。

最佳的电子邮件验证正则表达式

[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?

这是用法:-

bool isEmail = Regex.IsMatch(emailString, @"\A(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?)\Z", RegexOptions.IgnoreCase);

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
        );
    }

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。

这段代码将有助于在c#.Net中使用正则表达式验证电子邮件id。它很容易使用

if (!System.Text.RegularExpressions.Regex.IsMatch("<Email String Here>", @"^([\w\.\-]+)@([\w\-]+)((\.(\w){2,3})+)$"))
        {
            MessageBox.show("Incorrect Email Id.");
        }