Can I get the custom error message used with data annotation on controller MVC?

Question

Given a simplified class, like below:

public class Cliente
{
    [Display(Name = "Usuário")]
    [Required(ErrorMessage = "Informe um nome de usuário")]
    [EmailAddress(ErrorMessage = "Informe um e-mail válido")]
    [Remote("verificarUsernameCadastrado", "Validate", HttpMethod = "POST")]
    public String Username { get; set; }
}

I'm relatively new on the MVC world and I was thinking.. Is there a way to get, in the controller, the custom error message used with data annotation?

For instance, if I access the property Username in an action, I'd like to get the error message that I gave for EmailAddress (in this case, "Informe um e-mail válido").

I can easily duplicate this message where I want to use, but I'd really like to know if it's possible to do that.

Thanks in advance!

Mathew Thompson · Accepted Answer · 2015-02-09 13:10:22Z

4

You can do this using reflection, better used as an extension method:

public static T GetAttribute<T>(this object instance, string propertyName) where T : Attribute
{
    var attrType = typeof(T);
    var property = instance.GetType().GetProperty(propertyName);
    return (T)property .GetCustomAttributes(attrType, false).First();
}

Usage:

var errorMessage = client.GetAttribute<EmailAddressAttribute>("Username").ErrorMessage;

answered Feb 9, 2015 at 13:10

Mathew Thompson

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1 Comment

Everton Lenger Over a year ago

That is exactly what I was looking for. That's why Stack Overflow is so great. Thanks a lot!

markpsmith · Accepted Answer · 2015-02-09 13:11:43Z

2

You can get this from the ModelState when you POST to the controller method:

public ActionResult MyMethod(model MyModel)
{
    if (ModelState.IsValid)
    {
         // normal processing
    }
    else
    {
        if (ModelState["Username"].Errors.Count > 0)
        {
            var msg = ModelState["Username"].Errors[0].ErrorMessage;
        }
    }
}

answered Feb 9, 2015 at 13:11

markpsmith

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1 Comment

Everton Lenger Over a year ago

Yeah, I've used this already. But in the current case, my model is null, so the ModelState doesn't have any errors. That's why I wanna directly get the custom error message that I gave. In any case, I upvoted your answer as I consider it useful. :)

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