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

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;
    }
}

其他回答

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]

For the simple email like goerge@xxx.com, below code is sufficient. 

 public static bool ValidateEmail(string email)
        {
            System.Text.RegularExpressions.Regex emailRegex = new System.Text.RegularExpressions.Regex(@"^([\w\.\-]+)@([\w\-]+)((\.(\w){2,3})+)$");
            System.Text.RegularExpressions.Match emailMatch = emailRegex.Match(email);
            return emailMatch.Success;
        }

我从第1条中得到Phil的答案,并创建了这个类。 这样调用它:bool isValid = Validator.EmailIsValid(emailString);

下面是这个类:

using System.Text.RegularExpressions;

public static class Validator
{

    static Regex ValidEmailRegex = CreateValidEmailRegex();

    /// <summary>
    /// Taken from http://haacked.com/archive/2007/08/21/i-knew-how-to-validate-an-email-address-until-i.aspx
    /// </summary>
    /// <returns></returns>
    private static Regex CreateValidEmailRegex()
    {
        string validEmailPattern = @"^(?!\.)(""([^""\r\\]|\\[""\r\\])*""|"
            + @"([-a-z0-9!#$%&'*+/=?^_`{|}~]|(?<!\.)\.)*)(?<!\.)"
            + @"@[a-z0-9][\w\.-]*[a-z0-9]\.[a-z][a-z\.]*[a-z]$";

        return new Regex(validEmailPattern, RegexOptions.IgnoreCase);
    }

    internal static bool EmailIsValid(string emailAddress)
    {
        bool isValid = ValidEmailRegex.IsMatch(emailAddress);

        return isValid;
    }
}

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;
        }

如果你正在使用FluentValidation,你可以写一些像这样简单的东西:

public cass User
{
    public string Email { get; set; }
}

public class UserValidator : AbstractValidator<User>
{
    public UserValidator()
    {
        RuleFor(x => x.Email).EmailAddress().WithMessage("The text entered is not a valid email address.");
    }
}

// Validates an user. 
var validationResult = new UserValidator().Validate(new User { Email = "açflkdj" });

// This will return false, since the user email is not valid.
bool userIsValid = validationResult.IsValid;