ASP.NET MVC Data annotation validator for email or phone

Question

I am working on a form registration for ApplicationUser. There, I have a field Email or phone like Facebook. I am using DataAnnotation for model validation. In Data annotation I get [EmailAddress] for email validation and [Phone] for phone number validation. But I need something like [EmailAddressOrPhone]. So how I can achieve that?

public class RegisterViewModel
{
    .....

    [Required]
    [Display(Name = "Email or Phone")]
    public string EmailOrPhone { get; set; }

    ......
}

Answer 1

You shouldn't use your own regex to validate email addresses, however I personally would be using the following logic to determine if it is a valid email address. If it isn't a valid email address, you can assume it's a phone number.

The following code uses the [EmailAddress] attribute that you've already mentioned, but within the code. This way you don't have to invent your own way of validating the email address.

public EmailOrPhoneAttribute : ValidationAttribute
{
    public override IsValid(object value)
    {
        var emailOrPhone = value as string;

        // Is this a valid email address?
        if (this.IsValidEmailAddress(emailOrPhone))
        {
           // Is valid email address
           return true;
        }
        else if (this.IsValidPhoneNumber(emailOrPhone))
        {
            // Assume phone number
            return true;
        }

        // Not valid email address or phone
        return false;
    }

    private bool IsValidEmailAddress(string emailToValidate)
    {
        // Get instance of MVC email validation attribute
        var emailAttribute = new EmailAddressAttribute();

        return emailAttribute.IsValid(emailOrPhone);
    }

    private bool IsValidPhoneNumber(string phoneNumberToValidate)
    {
        // Regualr expression from https://stackoverflow.com/a/8909045/894792 for phone numbers
        var regex = new Regex("^\+?(\d[\d-. ]+)?(\([\d-. ]+\))?[\d-. ]+\d$");
        return regex.IsMatch(phoneNumberToValidate)
    }
}

Naturally you will need to determine how you are going to determine if the phone number is correct yourself, because phone numbers are different in different countries. I've just taken a regular expression from this question as an example.

Answer 2

You can achieve this using Regex. You have to combine the regex for email and phone together.

public class RegisterViewModel
{
    [Required]
    [Display(Name = "Email or Phone")]
    /* /<email-pattern>|<phone-pattern>/ */
    [RegularExpression(@"^([\w\.\-]+)@([\w\-]+)((\.(\w){2,3})+)$|^\+?\d{0,2}\-?\d{4,5}\-?\d{5,6}", ErrorMessage = "Please enter a valid email address or phone number")]      
    public string EmailOrPhone { get; set; }
}

Or You can create a custom attribute

 public class EmailOrPhoneAttribute : RegularExpressionAttribute
 {
    public EmailOrPhoneAttribute()
        : base(@"^([\w\.\-]+)@([\w\-]+)((\.(\w){2,3})+)$|^\+?\d{0,2}\-?\d{4,5}\-?\d{5,6}")
    {
        ErrorMessage = "Please provide a valid email address or phone number";
    }
 }

and use that

 public class RegisterViewModel
 {
    [Required]
    [Display(Name = "Email or Phone")]
    [EmailOrPhone]    
    public string EmailOrPhone { get; set; }
 }

Answer 3

In addition to custom attributes, you can have a look to this library: https://github.com/jwaliszko/ExpressiveAnnotations

An example is:

[Required]
[AssertThat("IsEmail(EmailOrPhone) || (Length(EmailOrPhone) > 8 && Length(EmailOrPhone) < 16 && IsRegexMatch(EmailOrPhone, '^\\d+$'))",
    ErrorMessageResourceType = typeof (Resources), ErrorMessageResourceName = nameof(Resources.EmailFormatInvalid))]
[Display(Name = "EmailOrPhone")]
public string EmailOrPhone { get; set; }

where I have used AssertThat attribute from ExpressiveAnnotations and created a error message EmailFormatInvalid in a Resources file.