一，当项目中存在多个网站报错，而不是新增Area出现这个错误时。应该在RouteConfig这样改：

using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Web.Mvc;using System.Web.Routing;namespace Houtai.Web.Mobile{    public class RouteConfig    {        public static void RegisterRoutes(RouteCollection routes)        {            routes.IgnoreRoute("{resource}.axd/{*pathInfo}");            routes.MapRoute(                name: "Default",                url: "{controller}/{action}/{id}",                defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional },                namespaces: new string[] { "Houtai.Web.Mobile.Controllers" }            );        }    }}

二，若是添加Area,造成的错误，则

public class RouteConfig    {        public static void RegisterRoutes(RouteCollection routes)        {            routes.IgnoreRoute("{resource}.axd/{*pathInfo}");           routes.MapRoute(                  "Default", // 路由名称                  "{controller}/{action}/{id}", // 带有参数的 URL                  new { controller = "Home", action = "Index", id = UrlParameter.Optional } // 参数默认值                  ,  new string[] { "Houtai.Web.Mobile.Controllers" }            );                       }    }