命名空间“System.Web”中不存在类型或命名空间名称“Optimization”解决方法

using System.Web.Optimization;

public class BundleConfig
{
public static void RegisterBundles(BundleCollection bundles)
{
bundles.Add( new StyleBundle( " ~/bundles/news.css ")
.Include( " ~/common/screen_base.css ",
" ~/common/screen_news.css "));

bundles.Add( new ScriptBundle( " ~/bundles/news.js ")
.Include( " ~/script/news_common.js ",
" ~/script/detail.js ",
" ~/script/share.js "));
}
}