将输入到数据库的电子邮件地址与数据注释进行比较

Question

我在MVC的模型中有一个类：

public class NewModel
{
    public bool AllComplexes { get; set; }
    public int UserID { get; set; }
    public int? RoleID { get; set; }
    public int ComplexID { get; set; }
    [Required(ErrorMessage = "Please enter a user name."), StringLength(50)]
    public string Username { get; set; }
    [Required(ErrorMessage = "Please enter Password"), StringLength(100, ErrorMessage = "Password cannot be longer than 100 characters")]
    public string Password { get; set; }
    [Compare("Password", ErrorMessage = "Passwords do not match")]
    [Required(ErrorMessage = "Please confirm Password")]
    public string RetypePassword { get; set; }
    [RegularExpression( "^[a-z0-9_\+-]+(\.[a-z0-9_\+-]+)*@[a-z0-9-]+(\.[a-z0-9]+)*\.([a-z]{2,4})$" , ErrorMessage = "Invalid email format." )]
    [Required(ErrorMessage = "Please enter your e-mail address."), StringLength(50)]
    public string Email { get; set; }
    public List<NEWCategoryModel> Categories { get; set; }
    //public List<NEWPrivilegeModel> userPrivList { get; set; }
    public List<DropDownItem> ComplexList { get; set; }
    public List<DropDownItem> RoleList { get; set; }
    public string NewRole { get; set; }
    public NewModel()
    {
    }
}

输入的电子邮件地址存储在 ：

    public string Email { get; set; }

我需要使用该数据注释将该电子邮件地址与存储在数据库中的所有电子邮件地址进行比较。我想我需要自定义数据注释？但我不知道该怎么做。

以下是从数据库中获取所有电子邮件地址的查询示例：

  db.ContactInformations.Where(x => x.EMail != null).Select(x => x.EMail);

Answer 1

public class NewModel 
{
      [EmailValidation(ErrorMessage = "The Email Address already exists")]
      [RegularExpression( "^[a-z0-9_\+-]+(\.[a-z0-9_\+-]+)*@[a-z0-9-]+(\.[a-z0-9]+)*\.([a-z]{2,4})$" , ErrorMessage = "Invalid email format." )]
      [Required(ErrorMessage = "Please enter your e-mail address."), StringLength(50)]
      public string Email { get; set; }
{

public class EmailValidation : ValidationAttribute
{
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        PropmetEntities db = new PropmetEntities();
        if (value != null)
        {
            var valueAsString = value.ToString();
            IEnumerable<string> email = db.ContactInformations.Where(x => x.EMail != null).Select(x => x.EMail);
            if (email.Contains(valueAsString))
            {
                var errorMessage = FormatErrorMessage(validationContext.DisplayName);
                return new ValidationResult(errorMessage);
            }
        }
        return ValidationResult.Success;
    }
}

Answer 2

这可以帮助您创建自定义验证。然后，要通过电子邮件检查数据库中是否已存在用户，请尝试：

bool exist = db.UserTable.Any(e => e.Email.ToLower() == emailValue.ToLower());

Answer 3

在这篇文章中，您将找到一个利用FluentValidation的解决方案，该解决方案实现了自定义DataAnnotation。

您的唯一电子邮件验证将如下所示：

[Validator(typeof(NewModelValidator))]
class NewModel
{
    //...Model implementation omitted
}
public class NewModelValidator : AbstractValidator<NewModel>
{
    public NewModelValidator()
    {
        RuleFor(x => x.Email).Must(IsUnieuqEmail).WithMessage("Email already exists");
    }
    private bool IsUniqueEmail(string mail)
    {
        var _db = new DataContext();
        if (_db.NewModel.SingleOrDefault(x => x.Email == mail) == null) return true;
        return false;
    }
}