Estou preenchendo três caixas suspensas na minha filterToolbar com dados do servidor, mostrados na declaração de prodValues, envValues ​​e typeValues ​​abaixo. Gostaria de alterar meu código para executar essa operação no evento beforeProcessing e extrair os valores do dump de dados da grade principal. Eu já tenho o servidor enviando o que eu acho que é a resposta json adequada para fazer isso:

{
   "pVals":"Product1:Product1;Product2:Product2;etc:etc",
   "eVals":"??:??;Dev:Dev;PreProd:PreProd;Prod:Prod;Test/QA:Test/QA",
   "tVals":"??:??;App:App;Service:Service;SQL:SQL;Web:Web",
   "page":0,
   "total":0,
   "records":537,
   "rows":[ /* many rows */
    ]
}

Como posso escolher as strings pVals, eVals e tVals no evento beforeProcessing e colocá-las nas caixas de seleção filterToolbar correspondentes?

Aqui está o meu código de grade para referência, com minhas tentativas quebradas de resolver este problema comentadas:

$(function () {
            var grid = $("#PSGrid");

            var pVals, eVals, tVals;

            // get values from Products table
            var prodValues = $.ajax({
                url: "jqGridHandler.ashx?oper=pVals",
                async: false,
                success: function (data) {

                }
            }).responseText;

            // get values from Environments table
            var envValues = $.ajax({
                url: "jqGridHandler.ashx?oper=eVals",
                async: false,
                success: function (data) {

                }
            }).responseText;

            // get values from ServerTypes table
            var typeValues = $.ajax({
                url: "jqGridHandler.ashx?oper=tVals",
                async: false,
                success: function (data) {

                }
            }).responseText;

            var lastsel = -1;

            // build the grid
            grid.jqGrid({
                url: 'jqGridHandler.ashx',
                editurl: 'jqGridEditor.ashx',
                datatype: 'json',
                height: 550,
                width: 'auto',
                colNames: ['ID', 'Product', 'Environment', 'Hostname', 'IP', 'Description', 'Type', 'PortsUsed', 'DeletedFlag', 'Decommissioned', 'User'],
                colModel: [
                    { name: 'ID', index: 'ID', width: 50, sortable: true, hidden: true, editable: false, key: true, sorttype: 'int' },
                    {
                        name: 'Product', index: 'Product', width: 125, sortable: true, editable: true,
                        stype: 'select', searchoptions: { value: ':All;' + prodValues, sopt: ['eq'] },
                        formatter: 'select', edittype: 'select', editoptions: { value: prodValues },
                        editrules: { required: true }
                    },
                    {
                        name: 'Environment', index: 'Environment', width: 100, sortable: true, editable: true,
                        stype: 'select', searchoptions: { value: ':All;' + envValues, sopt: ['eq'] },
                        formatter: 'select', edittype: 'select', editoptions: { value: envValues },
                        editrules: { required: true }
                    },
                    {
                        name: 'Hostname', index: 'Hostname', width: 200, sortable: true, editable: true,
                        editrules: { required: true }
                    },
                    {
                        name: 'IP', index: 'IP', width: 125, sortable: false, editable: true
                    },
                    {
                        name: 'Description', index: 'Description', width: 200, sortable: true, editable: true,
                        editrules: { required: true }
                    },
                    {
                        name: 'Type', index: 'Type', width: 75, sortable: true, editable: true,
                        stype: 'select', searchoptions: { value: ':All;' + typeValues, sopt: ['eq'] },
                        formatter: 'select', edittype: 'select', editoptions: { value: typeValues },
                        editrules: { required: true }
                    },
                    { name: 'PortsUsed', index: 'PortsUsed', width: 80, sortable: false, editable: true },
                    { name: 'DeletedFlag', index: 'DeletedFlag', hidden: true, searchoptions: { sopt: ['eq'], searchhidden: true }},
                    {
                        name: 'Decommissioned', index: 'DeletedFlag', width: 150, sortable: false, editable: false,
                        stype: 'select', searchoptions: { value: 'FALSE:No;TRUE:Yes' }/*, sorttype: 'date', datefmt: 'M/d/Y H:i:s A'*/
                    },
                    { name: 'User', index: 'User', width: 75, sortable: true, editable: false }
                ],
                rowNum: 10000, // show all rows hack (-1 is the proper way to do it but is bugged in this version of jqGrid)
                pager: '#PSGridPager',
                sortname: 'ID',
                pgbuttons: false,
                pgtext: null,
                viewrecords: false,
                sortorder: 'asc',
                ignoreCase: true,
                caption: 'Click a row to edit.  [Enter] to save, [Esc] to cancel.',
                loadonce: true,
                /*jsonReader: {
                    pVals: "pVals",
                    eVals: "eVals",
                    tVals: "tVals"
                },*/
                onSelectRow: function (id) {
                    if (id && id !== lastsel) {
                        grid.jqGrid('restoreRow', lastsel);
                        lastsel = id;
                    }
                    grid.jqGrid('editRow', id, true);
                },

                /*beforeProcessing: function (data) {
                    var pVals = data.pVals;
                    grid.setColProp('Product', {
                        index: 'Product', width: 125, sortable: true, editable: true,
                        stype: 'select', searchoptions: { value: ':All;' + pVals, sopt: ['eq'] },
                        formatter: 'select', edittype: 'select', editoptions: { value: pVals },
                        editrules: { required: true }
                    });
                }*/
            });

            grid.jqGrid('filterToolbar', { stringResult: true, searchOnEnter: true, defaultSearch: "cn" });
            grid.jqGrid('navGrid', '#PSGridPager', { edit: false, add: true, del: true, search: false, refresh: true, paging: false },
                { /* edit options */ },
                { /* add options */
                    closeOnEscape: true,
                    closeAfterAdd: true,
                    reloadAfterSubmit: true,
                    width: 400
                },
                { /* delete options */
                    closeOnEscape: true,
                    reloadAfterSubmit: true
                });
            grid.jqGrid('navButtonAdd', '#PSGridPager', {
                caption: "Export to Excel",
                onClickButton: function () {
                    grid.jqGrid('excelExport', { url: "jqGridHandler.ashx" });
                }
            });
        });

Se eu tentar usar beforeProcessing como está, a coluna Product não exibirá um filtro e não mostrará dados.