MVC - Custom Validate Checkbox - Get checkbox value in JavaScript (client)

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1. Validation 

        public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)

        {

            var rule = new ModelClientValidationRule

            {

                ValidationType = "validatecheckbox",

                ErrorMessage = "Fix it!"

            };

            rule.ValidationParameters.Add("fields", string.Join(",", _fields));

            yield return rule;

        }

2. JS

$.validator.addMethod('validatecheckbox', function (value, element, params) {

    debugger

    var isValid = true;

    if ($(params)[0].fields[1].val() == "True"){

        if ($(params)[0].fields[0][0].checked == false) {

            isValid = false;

        }

    }

});