Compare Email Address entered to database with DataAnnotations
asp.net-mvc, c#, data-annotations, email, modelstate
Solution
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})$" , ErrorMessage = "Invalid email format." )]
[Required(ErrorMessage = "Please enter your e-mail address."), StringLength(50)]
public string Email { get; set; }
{
public class EmailValidation : ValidationAttribute
{
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
PropmetEntities db = new PropmetEntities();
if (value != null)
{
var valueAsString = value.ToString();
IEnumerable<string> email = db.ContactInformations.Where(x => x.EMail != null).Select(x => x.EMail);
if (email.Contains(valueAsString))
{
var errorMessage = FormatErrorMessage(validationContext.DisplayName);
return new ValidationResult(errorMessage);
}
}
return ValidationResult.Success;
}
}
Problem
I have a class in my model in MVC: ``` public class NewModel { public bool AllComplexes { get; set; } public int UserID { get; set; } public int? RoleID { get; set; } public int ComplexID { get; set; } [Required(ErrorMessage = "Please enter a user name."), StringLength(50)] public string Username { get; set; } [Required(ErrorMessage = "Please enter Password"), StringLength(100, ErrorMessage = "Password cannot be longer than 100 characters")] public string Password { get; set; } [Compare("Password", ErrorMessage = "Passwords do not match")] [Required(ErrorMessage = "Please confirm Password")] public string RetypePassword { get; set; } [RegularExpression( "^[a-z0-9_\\+-]+(\\.[a-z0-9_\\+-]+)*@[a-z0-9-]+(\\.[a-z0-9]+)*\\.([a-z]{2,4})$" , 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() { } } ``` The Email address entered is stored in : ``` public string Email { get; set; } ``` I need to compare that Email address to all the email addresses stored in the database using Data Annotation. I assume I will need a Custom Data Annotation? But I have no idea how to do it. This is an example of the query to get al the email addresses from the database: ``` db.ContactInformations.Where(x => x.EMail != null).Select(x => x.EMail); ```