Client-side custom data annotation validation

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MVC4

Hi friends,
I had a requirement, where I need to check one value is always greater than other.
I have created a custom data annotation as follows:

using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Web.Mvc;

namespace AmericanExpress.GFES.INXSOnlineAdmin.WP.CustomValidation
{
    public class GreaterThanAttribute : ValidationAttribute, IClientValidatable
    {
        public string PropertyNameToCompare { get; set; }
        public string ErrorMessage { get; set; }

        public GreaterThanAttribute(string propertyNameToCompare, string errorMessage)
        {
            PropertyNameToCompare = propertyNameToCompare;
            ErrorMessage = errorMessage;
        }

        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            var propertyToCompare = validationContext.ObjectType.GetProperty(PropertyNameToCompare);
            if (propertyToCompare == null)
            {
                return new ValidationResult(
                    string.Format("Invalid property name '{0}'", PropertyNameToCompare));
            }
            var valueToCompare = propertyToCompare.GetValue(validationContext.ObjectInstance, null);

            bool valid;

            if (value is decimal && valueToCompare is decimal)
            {
                valid = ((decimal)value) > ((decimal)valueToCompare);
            }
            //TODO: Other types
            else
            {
                return new ValidationResult("Compared properties should be numeric and of the same type.");
            }

            if (valid)
            {
                return ValidationResult.Success;
            }

            return new ValidationResult(
                string.Format("{0} must be greater than {1}",
                    validationContext.DisplayName, PropertyNameToCompare));
        }

        public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
        {
            var rule = new ModelClientValidationRule();

            rule.ErrorMessage = ErrorMessage;
            rule.ValidationParameters.Add("other", PropertyNameToCompare);
            rule.ValidationType = "greaterthan";

            yield return rule;
        }
    }
}

In Model:

[Required(ErrorMessage = "Please enter minimum range")]
        public decimal RangeMin { get; set; }

        [Required(ErrorMessage = "Please enter maximum range")]
        [GreaterThan("RangeMin","Max range must be greater than Min")]
        public decimal RangeMax { get; set; }

In Partial View:

<script>
        $(document).ready(function () {
            $.validator.unobtrusive.parse("#frmSavePromotion");

            $.validator.addMethod('greaterthan', function (value, element) {
                return $(element).is(":checked");
            });

            $.validator.unobtrusive.adapters.add('greaterthan', [], function (options) {
                options.messages['greaterthan'] = options.message;
                options.rules['greaterthan'] = options.params;
            });
        });
    </script>

I have tried above, but it is working for me.

Can anyone tell me where I'm going wrong?

Thanks in advance