Why Does My ASP.NET MVC jqGrid Dropdown Show an 'Undefined' Value?

Resolving the "undefined" Value in ASP.NET MVC jqGrid Dropdowns

When dynamically populating jqGrid dropdowns during data editing, an unwanted "undefined" value frequently appears. This stems from inconsistencies between the data structure jqGrid expects and the data delivery method.

Correct jqGrid Data Format:

The ideal format for the dropdown's value is: value: "FE:FedEx; IN:InTime; TN:TNT"

Problem with Current Method:

The current approach uses ASP.NET MVC with jQuery's $.ajax() to fetch dropdown data. A StringBuilder manipulates the retrieved data to match jqGrid's format, but an extra "undefined" entry persists.

Debugging Findings:

FireBug debugging indicates that extra quotes introduced by sb.ToString() are the culprit. jqGrid adds its own quotes, leading to doubled-up quotes and the "undefined" issue.

A Superior Solution: Using dataUrl and buildSelect

Instead of directly manipulating the value property, a more robust solution involves using jqGrid's dataUrl and buildSelect properties within editoptions or searchoptions. These allow for customized data fetching and formatting.

Example dataUrl Action:

<code class="language-csharp">public JsonResult GetDestinationList() {
    List<string> allDestinations = GetAllDestinations();
    return Json(allDestinations, JsonRequestBehavior.AllowGet);
}</code>

Example buildSelect Function:

<code class="language-javascript">buildSelect: function(data) {
    var s = '';
    if (data && data.length) {
        for (var i = 0, l = data.length; i < l; i++) {
            s += data[i] + ';'; // Assuming data[i] is already in "key:value" format
        }
        return s.substring(0, s.length - 1); // Remove trailing semicolon
    }
    return s;
}</code>

Updated editoptions:

<code class="language-javascript">{
    name: 'destinations',
    editable: true,
    edittype: 'select',
    editoptions: {
        dataUrl: '/YourController/GetDestinationList', // Replace with your controller action path
        buildSelect: function(data) {
            // ... (buildSelect function from above) ...
        }
    }
}</code>

Important Notes:

• You can use Json(allDestinations); without JsonRequestBehavior.AllowGet, but you'll need to add ajaxSelectOptions: { type: "POST" } to your jqGrid options.
• In newer jqGrid versions, buildSelect is called within the $.ajax() success handler, making jQuery.parseJSON(data.responseText) unnecessary.

This revised approach provides a cleaner, more efficient, and less error-prone method for managing jqGrid dropdowns, eliminating the "undefined" value issue. Remember to replace /YourController/GetDestinationList with the actual path to your controller action.

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