Checking Request.IsAjaxRequest always return false inside my asp.net mvc4

I have the following code inside my controller ``` public ActionResult Index(string searchTerm=null) { System.Threading.Thread.Sleep(5000); var accountdefinition = repository.FindAccountDefinition(searchTerm).ToList(); if (Request.IsAjaxRequest()) { return PartialView("_CustomerTable",accountdefinition); } return View(accountdefinition); } ``` But if I call the above action method using an Ajax.beginform,, then the Request.IsAjaxRequest will return false and the partial view will not be returned ``` @using (Ajax.BeginForm( new AjaxOptions{ HttpMethod= "get", InsertionMode=InsertionMode.Replace, LoadingElementId = "progress", UpdateTargetId="customerTable"})) { <div style="float:right">Search <input placeholder="Search by name.." name="searchTerm" type="text"> <input class="btn btn-success" type="submit" value="search" /></div> } <div id = "progress" class="loadingimage"> <img src="~/Content/Ajax-loader-bar.gif" /> </div> ```