Question

How can I write the validation using data annotation in writing telephone number such as “094-4567” or mobile number such as “09129705678” etc.?

using System.Web;
using System.Data.Entity;
using System.ComponentModel.DataAnnotations;

namespace PhoneBook.Models
{
    public class Contact
    {
        [Required(ErrorMessage="Telephone Number Required")
        [?]
        public string Telephone Number {get; set;}
    }
}

I really don’t know what to do…

Answer 1

You can use regular expression attribute like so:

namespace PhoneBook.Models
{
    public class Contact
    {
        [Required(ErrorMessage="Telephone Number Required")
        [RegularExpression(@"^\(?([0-9]{3})\)?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$", ErrorMessage = "Entered phone format is not valid.")]
        public string Telephone Number {get; set;}
    }
}

It will match numbers like: 0123456789, 012-345-6789, [phone] etc.

You can learn more about this expression here: How to use Regular expression for validating Phone Numbers