Client-side validation does not work when inherting from RequiredAttribute in ASP.NET MVC 3?

Question

I created an inherited attribute like this in ASP.NET MVC3:

public sealed class RequiredFromResourceAttribute : RequiredAttribute
{
    public RequiredFromResourceAttribute(string errorResourceName, string errorResourceTypeName)
    {
        this.ErrorMessageResourceName = errorResourceName;
        this.ErrorMessageResourceType = Type.GetType(errorResourceTypeName);
    }
}

And use it like this:

[RequiredFromResource("Title", "Resources.Resource, MyProject.Mvc, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null")]
public string Title { get; set; }

It didn't work and the MVC ignored it. Then I create a simpler class which just inherited from RequiredAttribute like this:

public class MyRequiredAttribute : RequiredAttribute
{
}

I use it like that I said. But it didn't work again.

Although, all these ways work on "DisplayNameAtrribute" perfectly.

What is the problem?

Answer 1

You can fix this by adding the following code in Global.asax: (found the answer here)

DataAnnotationsModelValidatorProvider.RegisterAdapter(typeof(RequiredLocalizableAttribute), typeof(RequiredAttributeAdapter));

Alternatively, using marcind's solution, I found that the constructor for ModelClientValidationRequiredRule requires an error message. Here is an updated version that includes the display name for the field:

    public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
    {
        string msg = FormatErrorMessage(metadata.GetDisplayName());
        yield return new ModelClientValidationRequiredRule(msg);
    }

Answer 2

It's only client-side validation that does not work with inherited attributes. The reason for that is that MVC uses strict type equality when mapping server-side attributes to client validation behaviors.

To work around this you will need your custom attribute to implement IClientValidatable:

public class MyRequiredAttribute : IClientValidatable {
    public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context) {
         yield return new ModelClientValidationRequiredRule();
    }
}