How to set unobtrusive validation for UI elements rendered using jQuery

Question

I have a Razor view which renders some drops downs using HTML helpers and others using jQuery DataTable,

<div class="form-group">
            @Html.LabelFor(model => model.CarTyres, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-2">
                @Html.ListBoxFor(model => model.SelectedCarTyres, Model.CarTyres, htmlAttributes: new { @class = "selectpicker form-control", @multiple = "", @data_actions_box = "true" })
                @Html.ValidationMessageFor(model => model.SelectedCarTyres, "", new { @class = "text-danger" })

            </div>
        </div>
        <div class="form-group">
            @Html.LabelFor(model => model.Drivers, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-2">
                @Html.ListBoxFor(model => model.SelectedDrivers, Model.Drivers, htmlAttributes: new { @class = "selectpicker form-control", @multiple = "", @data_actions_box = "true" })
                @Html.ValidationMessageFor(model => model.SelectedDrivers, "", new { @class = "text-danger" })
            </div>
        </div>
        <div class="form-group">
            @Html.LabelFor(model => model.CarJacks, htmlAttributes: new { @class = "control-label col-md-2" })

            <div class="col-md-5">
                <table id="filtersTable">
                    <thead>
                        <tr>
                            <th>Select</th>
                            <th>Name</th>
                        </tr>
                    </thead>
                </table>
            </div>
            @Html.ValidationMessageFor(model => model.CarJacksCheckBox, "", new { @class = "text-danger" })
        </div>

In my model , I am setting the required to true so that when I check Model.IsValid() will return false if any of those items are not set, and that works fine.

  public class ReportViewModel
    {
        public DateTime StartTime { get; set; }
        public DateTime EndTime { get; set; }


        [Required]
        public ICollection<int> SelectedCarTyres { get; set; }
        public IEnumerable<SelectListItem> CarTyres { get; set; }

        [Required]
        public ICollection<int> SelectedDrivers { get; set; }
        public IEnumerable<SelectListItem> Drivers { get; set; }


        public IEnumerable<CarJackViewModel> CarJacks { get; set; }

        [Required]
        public string SelectedSampleTime { get; set; }
        public IEnumerable<SelectListItem> SampleTimes { get; set; }



        [Required]
        public IEnumerable<int> CarJacksCheckBox { get; set; }


    }

To make javascrip data tables required , I copied the vallidation attributes on checkbox(es) like following:

 $('#filtersTable').DataTable(
        {
            "iDisplayLength": 25,
            "ajax": {
                "url": "/CarJacks/Loaddata",
                "type": "GET",
                "datatype": "json"
            },
            "columns": [
                {
                    "data": "IsSelected",
                    "render": function (data, type, row) {
                        if (type === 'display') {
                            return '<input type="checkbox" name="CarJacksCheckBox" class="editor-active" data-val="true"  data-val-required="The CarJacks field is required.">';
                        }
                        return data;
                    }

            ],
            "rowCallback": function (row, data) {
                //Removed for Brevity
            }
        }
    );

But still , I am not getting any client side validation when none of the CarJackCheckBox are selected.

Though (ModelState.IsValid) is returning false, $(form).valid() returning true and hence no errors on client side.

Which piece am I missing ?

Answer 1

You cannot use MVC's client side validation because validation rules are applied to form controls, and you do not (and cannot) create a form control for your IEnumerable<int> CarJacksCheckBox property. You need to write your own script to validate that at least one checkbox is required.

Remove the data-val-* attributes from the checkbox (since they are pointless) and add an additional class name, say carjacks to use in the script as a jQuery selector.

Then include the following scripts (note these mimic 'lazy' validation - it first validates on submit, and thereafter on clicking a checkbox)

var validateOnClick = false; // for lazy validation
var requiredCarJacks = 1;
var carJacks= $('.carjacks');
var errorMessage = 'Select at least 1 car jack';
var errorElement = $('span[data-valmsg-for="CarJacksCheckBox"]');

function validateCarJacks() {
    var selectedCarJacks = carJacks.filter(':checked').length;
    var isValid = selectedCarJacks > requiredCarJacks ;
    if (!isValid) {
        errorElement.addClass('field-validation-error').removeClass('field-validation-valid').text(errorMessage);
    } else {
        errorElement.addClass('field-validation-valid').removeClass('field-validation-error').text('');
    }
    return (isValid);
}

$('form').submit(function () {
    if (!validateCarJacks()) {
        validateOnClick = true; // signal that we should now validate the .click() event
        return false; // prevent submit
    }
});

carJacks.click(function() {
    if (validateOnClick) {
        validateCarJacks();
    }
})