MVC dropdownlist onchange call jquery

Question

I have a SelectList representing a delivery type for an order.

The delivery type reference data has the usual code/description, but also an additional boolean property which indicates if further information needs to be entered for the type selected.

So for Emergency deliveries additional data is required. The additional data entry fields would be set visible if Emergency was selected, otherwise hidden

My ViewModel contains <List>ReferenceDeliveryTypes which contains the 3 properties. I have created a SelectListItems from the ViewModel data

@Html.DropDownListFor(model => model.DeliveryTypeCode, 
    new SelectList(Model.ReferenceDeliveryTypes as System.Collections.IEnumerable, 
        "DeliveryTypeCode", "DeliveryTypeDescription"), new { id = "ddlDeliveryType" })

How can I call a jQuery function on change of the delivery type, pass the selected code and check the Model.ReferenceDeliveryTypes for that code to see if the additional data property is true/false to show/hide the additional fields div?

I have managed to get the jQuery function called to pass the value.

$(function () {

$('#ddlDeliveryType').change(function () {
    var value = $(this).val();
    alert(value);
});

});

Solution 1

I don't know of any way you can do this using a select list but I suggest the following options:

• Simple but a hack - add a string to the end of DeliveryTypeDescription, for example (emergency delivery) and check for that in your change function
• Another hack - multiply DeliveryTypeCode by 10 and add 1 on if it's an emergency delivery (and then use mod 10 in your change function)
• Use an Ajax lookup function
• Load a JavaScript lookup table with the codes which require an emergency delivery
• Use a hidden field in your form which contains a string list of the emergency codes with a suitable separator

Good luck

UPDATE For the hidden field option if you use something like 123|456|789| and then use indexOf having appended a | to the selected ID.

Solution 2

I converted the Model.ReferenceDeliveryTypes to a JSON list which allowed me to access it from the jQuery.

Possibly not the best way, but it allows me to do everything on the client rather than making an AJAX call back. I can now show/hide the inside the if block.

Thought it worth documenting what I did as I've not come across the @Html.Raw(Json.Encode before and it might prove useful for someone who wants to access model data from within jQuery.

Any additional comments welcome.

        <script type="text/javascript">
            var [email protected](Json.Encode(Model.ReferenceDeliveryTypes))
        </script>



        @Html.DropDownListFor(model => model.DeliveryTypeCode,
                new SelectList(Model.ReferenceDeliveryTypes.ReferenceDeliveryType as System.Collections.IEnumerable,
                "DeliveryTypeCode", "DeliveryTypeDescription"), new { id = "ddlDeliveryType" })



$(function () {

    $('#ddlDeliveryType').change(function () {

        var selectedDT= $(this).val();

        $.each(ReferenceDeliveryTypeJsonList, function (index, item) {

            if (selectedDT === item.DeliveryTypeCode) {
                alert("match " + selectedDT);
            }

        });

    });
});

Comments

[MartinS]

The hidden field might be easiest. I was also considering serializing the Model.ReferenceDeliveryTypes as a JSON using @Html.Raw(Json.Encode(Model.ReferenceDeliveryTypes I could then use that in the jQuery. I've not managed it so far though.