MVC routes.RouteExistingFiles = true设置在开发环境下无效

[我是小数位]

    
 public static void RegisterRoutes(RouteCollection routes)
        {
            routes.RouteExistingFiles = true;

            routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
         
            routes.MapRoute(
                name: "Default",
                url: "{controller}/{action}/{id}",
                defaults: new { controller = "Index", action = "Index", id = UrlParameter.Optional }, namespaces: new[] { "Web.Controllers" }
            );

        }

配置文件设置如下
    <modules runAllManagedModulesForAllRequests="true">
    </modules>

IIS Express 配置如下：
              <add name="UrlRoutingModule-4.0" type="System.Web.Routing.UrlRoutingModule" preCondition="" />
                <!--<add name="UrlRoutingModule-4.0" type="System.Web.Routing.UrlRoutingModule" preCondition="managedHandler,runtimeVersionv4.0" />-->

经过以下配置，开发环境下，只要文件存在的，还是能返回。但是发布到IIS是好的，请问什么原因