$("form").submit(function () {         var flag;

         $.ajax({

             type: 'GET',

             url: "@Url.Action("action", "controller")",             //async: false,

             success: function (data) {

                 if (data == "S") {

                     swal("该种子品种+种子批次已经存在！请勿重复添加！！", data.Msg, "warning");

                     flag = false;

                 }

                 else {

                     flag = true;

                 }

             }

         });

         alert(flag);

         return flag;

     });