dataValueField String (default: "")

The field of the data item that provides the value of the widget.

If you define the dataValueField option, you also have to set dataTextField.

Example - set the dataValueField

<select id="listBox"></select>
<script>
$("#listBox").kendoListBox({
    dataSource: [
        { name: "Item 1", id: 1 },
        { name: "Item 2", id: 2 }
    ],
    dataTextField: "name",
    dataValueField: "id"
});
</script>