How to change the default ErrorMessage for StringLength attribute in view model with unobtrusive validation

Question

The default StringLength validation error message is too long for my purposes, so I would like to make it shorter.

I know I can specify the ErrorMessage for each property, but I rather not duplicate this all over the place:

[StringLength(25, ErrorMessage = "Max length is {1}")]
[DisplayName("Address")]
public virtual string BillAddress1 { get; set; }

Based on this post, Modify default ErrorMessage for StringLength validation, I subclassed StringLengthAttribute:

public class CustomStringLengthAttribute : StringLengthAttribute
{
    public CustomStringLengthAttribute()
        : this(20)
    {
    }

    public CustomStringLengthAttribute(int maximumLength)
        : base(maximumLength)
    {
        base.ErrorMessage = "Max length is {1}";
    }
}

And changed to use CustomStringLengthAttribute instead:

[CustomStringLength(25)]
[DisplayName("Address")]
public virtual string BillAddress1 { get; set; }

This compiles fine, and I set a breakpoint in the CustomStringLengthAttribute constructor to verify that it gets hit, but unobtrusive validation no longer works - invalid data gets posted back to the controller.

It works fine when I do not use my subclassed version.

Also, here is the javascript validation:

if (validation.validateForm($('#addressForm'))) {
    ....
}

validateForm:

function validateForm(form) {
    prepareValidationScripts(form);
    var validator = $.data(form[0], 'validator');
    return validator.form();
}

function prepareValidationScripts(form) {
    if (form.executed)
        return;
    form.removeData("validator");
    $.validator.unobtrusive.parse(document);
    form.executed = true;
}

What am I missing?

Thanks.

Answer 1

Try this having custom validation.

CustomStringLengthAttribute.cs

public class CustomStringLengthAttribute : ValidationAttribute, IClientValidatable
    {
        public int MaximumLength
        {
            get;
            private set;
        }
        public int MinimumLength
        {
            get;
            set;
        }
        public CustomStringLengthAttribute(int maximumLength)
            : base(new Func<string>(CustomStringLengthAttribute.GetDefaultErrorMessage))
        {
            this.MaximumLength = maximumLength;
        }
        private static string GetDefaultErrorMessage()
        {
            return "Max length {1}";
        }
        public override string FormatErrorMessage(string name)
        {
            return string.Format(base.ErrorMessageString, name, this.MaximumLength, this.MinimumLength);
        }
        public override bool IsValid(object value)
        {
            if (value == null)
            {
                return true;
            }
            string text = (string)value;
            int maximumLength = this.MaximumLength;
            int minimumLength = this.MinimumLength;
            if (maximumLength < 0)
            {
                throw new InvalidOperationException("The maximum length must be a nonnegative integer.");
            }
            if (minimumLength > maximumLength)
            {
                throw new InvalidOperationException(string.Format("The maximum value '{0}' must be greater than or equal to the minimum value '{1}'.", maximumLength, minimumLength));
            }
            int length = text.Length;
            return length <= maximumLength && length >= minimumLength;
        }

        public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
        {
            var rule = new ModelClientValidationRule();
            rule.ErrorMessage = FormatErrorMessage(metadata.GetDisplayName());
            rule.ValidationParameters.Add("max", MaximumLength);
            rule.ValidationParameters.Add("min", MinimumLength);
            rule.ValidationType = "customstringlength";
            yield return rule;
        }
    }

In js file:

/// <reference path="jquery-1.4.4.js" />
/// <reference path="jquery.validate.js" />
/// <reference path="jquery.validate.unobtrusive.js" />

if ($.validator && $.validator.unobtrusive) {

    $.validator.unobtrusive.adapters.addMinMax("customstringlength", "min","max");

    $.validator.addMethod("customstringlength", function (value, element, min,max) {
        if (value) {
            if (value.length<min || value.length>max) {
                return false;
            }
        }
        return true;
    });

}

Model class:

[CustomStringLength(25)]
[DisplayName("Address")]
public virtual string BillAddress1 { get; set; }