model-view-controller – 找不到类型或命名空间名称’ScriptBun

using System.Web;
using System.Web.Optimization;

bundles.Add(new ScriptBundle("~/bundles/jquery").Include(
                    "~/Scripts/jquery-{version}.js"));

        bundles.Add(new ScriptBundle("~/bundles/jqueryui").Include(
                    "~/Scripts/jquery-ui-{version}.js"));

        bundles.Add(new ScriptBundle("~/bundles/jqueryval").Include(
                    "~/Scripts/jquery.unobtrusive*","~/Scripts/jquery.validate*"));

我收到错误：

Error   16  The type or namespace name 'ScriptBundle' could not be found (are you missing a using directive or an assembly reference?)

看起来像一些参考问题,但我无法弄明白.请帮忙.可能导致此错误的原因是什么？