Allow empty string for EmailAddressAttribute

Question

I have property in my PersonDTO class:

[EmailAddress]
public string Email { get; set; }

It works fine, except I want to allow empty strings as values for my model, if I send JSON from client side:

{ Email: "" }

I got 400 bad request response and

{"$id":"1","Message":"The Email field is not a valid e-mail address."}

However, it allows omitting email value:

{ FirstName: "First", LastName: 'Last' }

I also tried:

[DataType(DataType.EmailAddress, ErrorMessage = "Email address is not valid")]

but it does not work.

As far as I understood, Data Annotations Extensions pack does not allow empty string either.

Thus, I wonder if there is a way to customize the standard EmailAddressAttribute to allow empty strings so I do not have to write custom validation attribute.

I dont think there is a work around for this issue so far. You might end up writing a custom attribute extending EmailAddress or else use Regex Attribute to validate valid email address and allow empty string. Reference - https://aspnetwebstack.codeplex.com/workitem/1112 — ramiramilu, May 05 '14 at 15:18
Possible Duplicate of - http://stackoverflow.com/questions/16098903/emailaddressattribute-without-being-required — ramiramilu, May 05 '14 at 15:31

Yishai Galatzer · Accepted Answer · 2017-09-08T17:16:59.083

You have two options:

Convert string.Empty to null on the Email field. Many times that is perfectly acceptable. You can make this work globally, or by simply making your setter convert string.Empty to null on the email field.
Write a custom EmailAddress attribute, since EmailAddressAttribute is sealed you can wrap it and write your own forwarding IsValid method.

Sample:

bool IsValid(object value)
{
    if (value == string.Empty)
    {
        return true;
    }
    else
    {
        return _wrappedAttribute.IsValid(value);
    }
}

Expansion on option 1 (from Web Api not converting json empty strings values to null)

Add this converter:

public class EmptyToNullConverter : JsonConverter
{
    private JsonSerializer _stringSerializer = new JsonSerializer();

    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(string);
    }

    public override object ReadJson(JsonReader reader, Type objectType,
                                    object existingValue, JsonSerializer serializer)
    {
        string value = _stringSerializer.Deserialize<string>(reader);

        if (string.IsNullOrEmpty(value))
        {
            value = null;
        }

        return value;
    }

    public override void WriteJson(JsonWriter writer, object value, 
                                   JsonSerializer serializer)
    {
        _stringSerializer.Serialize(writer, value);
    }
}

and use on the property:

[JsonConverter(typeof(EmptyToNullConverter))]
public string EmailAddress {get; set; }

or globally in WebApiConfig.cs:

config.Formatters.JsonFormatter.SerializerSettings.Converters.Add(
    new EmptyToNullConverter());

it's getting interesting, 1. I did not quite get how I can globally convert string empty to null? I got with using underlying field and setter/getter. cool idea, thanks 2. wrapper for sealed attribute? could you please show small example, I failed at googling it) thanks! — makambi, May 05 '14 at 15:46
Added how to convert globally or per properties. To wrap you need to create your own attribute, and make emailaddressattribute a member. Then instantiate the original emailaddressattribute in your constructor as well as make every property call the member. It's really straight forward C# at that point. If you need to search for specific example look for the decorator pattern or follow this link: http://stackoverflow.com/questions/2707401/please-help-me-understand-the-decorator-pattern-with-a-real-world-example/2707425#2707425 — Yishai Galatzer, May 05 '14 at 16:23

score 20 · Answer 2 · answered Jul 18 '19 at 01:17

20

It's Easy. Do This. Bye

private string _Email;
[EmailAddress(ErrorMessage = "Ingrese un formato de email válido")]
public string Email { get { return _Email; } set { _Email = string.IsNullOrWhiteSpace(value) ? null : value; } }

answered Jul 18 '19 at 01:17

Esteban Kito

578
5
4

Easy and best solution so far – EagerNoob Mar 15 '22 at 16:59

score 4 · Answer 3 · answered Apr 29 '22 at 14:15

I used the suggestion from Yishai Galatzer to make a new ValidationAttribute called EmailAddressThatAllowsBlanks:

namespace System.ComponentModel.DataAnnotations
{
    public class EmailAddressThatAllowsBlanks : ValidationAttribute
    {
        public const string DefaultErrorMessage = "{0} must be a valid email address";
        private EmailAddressAttribute _validator = new EmailAddressAttribute();

        public EmailAddressThatAllowsBlanks() : base(DefaultErrorMessage)
        {

        }

        public override bool IsValid(object value)
        {
            if (string.IsNullOrEmpty(value.ToString()))
                return true;

            return _validator.IsValid(value.ToString());
        }
    }
}

score 0 · Answer 4 · edited Aug 29 '20 at 19:26

0

Set TargetNullValue property of the binding to an empty string.

TargetNullValue=''

edited Aug 29 '20 at 19:26

Jeremy Caney

7,102
69
48
77

answered Aug 29 '20 at 19:10

Maqsood

11
2

Allow empty string for EmailAddressAttribute

4 Answers4