MaxLength Attribute not generating client-side validation attributes

Question

I have a curious problem with ASP.NET MVC3 client-side validation. I have the following class:

public class Instrument : BaseObject
{
    public int Id { get         


        

Answer 1

I know I am very late to the party, but I finaly found out how we can register the MaxLengthAttribute.

First we need a validator:

public class MaxLengthClientValidator : DataAnnotationsModelValidator
{
    private readonly string _errorMessage;
    private readonly int _length;


    public MaxLengthClientValidator(ModelMetadata metadata, ControllerContext context, MaxLengthAttribute attribute)
    : base(metadata, context, attribute)
    {
        _errorMessage = attribute.FormatErrorMessage(metadata.DisplayName);
        _length = attribute.Length;
    }

    public override IEnumerable GetClientValidationRules()
    {
        var rule = new ModelClientValidationRule
        {
            ErrorMessage = _errorMessage,
            ValidationType = "length"
        };

        rule.ValidationParameters["max"] = _length;
        yield return rule;
    }
}

Nothing realy special. In the constructor we save some values from the attribute. In the GetClientValidationRules we set a rule. ValidationType = "length" is mapped to data-val-length by the framework. rule.ValidationParameters["max"] is for the data-val-length-max attribute.

Now since you have a validator, you only need to register it in global.asax:

protected void Application_Start()
{
    //...

    //Register Validator
    DataAnnotationsModelValidatorProvider.RegisterAdapter(typeof(MaxLengthAttribute), typeof(MaxLengthClientValidator));
}

Et voila, it just works.