Adding your Custom validation in MVC 4 using Validation Attribute and unobtrusive Jquery library

1)  DEFINED YOUR PROPERTY IN MODEL CLASS ....

//DefaultReorderQuantity
        [Display(Name = "DefaultReorderQuantity", ResourceType = typeof(ResItemMaster))]
        [RegularExpression(@"^[0-9\.]*$", ErrorMessageResourceName = "InvalidValue", ErrorMessageResourceType = typeof(ResMessage))]
        [Required(ErrorMessageResourceName = "Required", ErrorMessageResourceType = typeof(ResMessage))]
        [DefaultReorderQuantityCheck("MaximumQuantity", ErrorMessage = "Default Reorder quantity must be less then Maximum quantity")]
        public System.Double DefaultReorderQuantity { get; set; }

 2) IN MODEL CREATE NEW CLASS WITH SAME NAME OF PROPERTY

[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, AllowMultiple = false)]
public class DefaultReorderQuantityCheckAttribute : ValidationAttribute, IClientValidatable
{
    private readonly string _MaxQTYFieldName;
    public DefaultReorderQuantityCheckAttribute(string MaxQtyFieldName)
    {
        _MaxQTYFieldName = MaxQtyFieldName;
    }
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        var property = validationContext.ObjectType.GetProperty(_MaxQTYFieldName);
        var otherPropertyValue = property.GetValue(validationContext.ObjectInstance, null);
        if (value != null)
        {
            double DefReQTY = (double)value;
            if (DefReQTY >= (double)otherPropertyValue)
            {
                ValidationResult Ok = new ValidationResult("Default Reorder quantity must be less then Maximum quantity");
                return Ok;
            }
        }
        return ValidationResult.Success;
    }
    public IEnumerable
           GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
    {
        yield return new ModelClientValidationRule
        {
            ErrorMessage = ErrorMessage,
            ValidationType = "defaultreorderquantity"
        };
    }
}


3)  IN YOUR VIEW ADD THIS LINES TO CHECK VALIDATION FROM CLIENT SIDE

$("form").submit(function (e) {
        $.validator.unobtrusive.parse("#frmItemMaster");
       
        if ($(this).valid()) {
                   }
        e.preventDefault();
    });   


4) ADD BELOW LINES TO ADD THE RULE OF VALIDATION IN unobtrusive  VALIDATION LIBRARY ....

jQuery.validator.addMethod('defaultreorderquantity', function (value, element, params) {
            if (parseInt(element.form.DefaultReorderQuantity.value == '' ? 0 : element.form.DefaultReorderQuantity.value, 10) >= parseInt(element.form.MaximumQuantity.value == '' ? 0 : element.form.MaximumQuantity.value, 10))
                return false;
            else
                return true;
        }, '');
        jQuery.validator.unobtrusive.adapters.add('defaultreorderquantity', {}, function (options) {
            options.rules['defaultreorderquantity'] = true;
            options.messages['defaultreorderquantity'] = options.message;
        });

5 ) CONTROLLER SIDE VALIDATION IF REQUIRED

if (!ModelState.IsValid)
            {
if (ModelState["DefaultReorderQuantity"].Errors.Count > 0)
                {
                    return Json(new { Message = ModelState["DefaultReorderQuantity"].Errors[0].ErrorMessage, Status = "Fa" }, JsonRequestBehavior.AllowGet);
                }
                else
                {
                    return Json(new { Message = ResMessage.InvalidModel, Status = "Fa" }, JsonRequestBehavior.AllowGet);
                }
            }

AND YOU ARE DONE.... USE THIS AS PER YOUR REQUIREMENT ... HERE FIELD DEFAULT REORDER QUANTITY IS AN EXAMPLE ...