关于javascript：我缺少什么来实现不区分大小写的搜索？

What I m missing to implement case insensitive search?

这是我的JS文件。我已经完成了服务器端的所有工作。实现了数据表插件的所有基本功能和一些高级功能。但是搜索功能是区分大小写的。如果我搜索"石油"，它只显示石油，而不是石油。

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$(document).ready(function () {
var oTable = $('#myDataTable').dataTable({
"bServerSide": true,
"sPaginationType":"full_numbers",
"sAjaxSource":"/DB/AjaxOil",
"bProcessing": true,
"Search": {
"caseInsensitive": true
},
"aoColumns": [
{
"sName":"OilId",
"aTargets": [0], //Edit column
"mData":"OilId",
"bSearchable": false,
"bSortable": false,
"mRender": function (data, type, full) {
var id = full[0]; //row id in the first column
return""+id+"";
}
},
{"sName":"CommonName" },
{"sName":"BotanicalName" },
{"sName":"PlantParts" },
{"sName":"Distillation" }
],
"columnDefs": [
{
"targets": [0],
className:"hide_column",
"searchable": false
}
]

});

(})；

这是我的Ajax函数

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public ActionResult AjaxOil(JQueryDataTableParamModel param)
{
IEnumerable<Oil> allOils = _context.Oils.ToList();
IEnumerable<Oil> filteredOils;
if (!string.IsNullOrEmpty(param.sSearch))
{
filteredOils = allOils
.Where(c => c.CommonName.Contains(param.sSearch)
||
c.BotanicalName.Contains(param.sSearch)
||
c.PlantParts.Contains(param.sSearch)
||
c.Distillation.Contains(param.sSearch));
}
else
{
filteredOils = allOils;
}

var sortColumnIndex = Convert.ToInt32(Request["iSortCol_0"]);
Func<Oil, string> orderingFunction = (c => sortColumnIndex == 1 ? c.CommonName :
sortColumnIndex == 2 ? c.BotanicalName :
c.PlantParts);

var distillationFilter = Convert.ToString(Request["sSearch_4"]);
var commonFilter = Convert.ToString(Request["sSearch_1"]);
var botanicalFilter = Convert.ToString(Request["sSearch_2"]);
var plantFilter = Convert.ToString(Request["sSearch_3"]);

if (!string.IsNullOrEmpty(commonFilter))
{
filteredOils = filteredOils.Where(c => c.CommonName.Contains(commonFilter));

}

if (!string.IsNullOrEmpty(botanicalFilter))
{
filteredOils = filteredOils.Where(c => c.BotanicalName.Contains(botanicalFilter));

}

if (!string.IsNullOrEmpty(plantFilter))
{
filteredOils = filteredOils.Where(c => c.PlantParts.Contains(plantFilter));

}

if (!string.IsNullOrEmpty(distillationFilter))
{
filteredOils = filteredOils.Where(c => c.Distillation.Contains(distillationFilter));

}

var sortDirection = Request["sSortDir_0"];
if (sortDirection =="asc")
filteredOils = filteredOils.OrderBy(orderingFunction);
else
filteredOils = filteredOils.OrderByDescending(orderingFunction);

var displayedOils = filteredOils
.Skip(param.iDisplayStart)
.Take(param.iDisplayLength);
var result = from c in displayedOils
select new[] { Convert.ToString(c.OilId), c.CommonName, c.BotanicalName, c.PlantParts, c.Distillation };
return Json(new
{
sEcho = param.sEcho,
iTotalRecords = allOils.Count(),
iTotalDisplayRecords = filteredOils.Count(),
aaData = result
},
JsonRequestBehavior.AllowGet);
}

P.S.数据库有500万行，请从性能角度提出建议。