ASP。netmvc 5路由在使用RouteArea之后停止工作

I've created a new ASP.NET MVC 5 using Visual Studio 2015. All the code in the project is default which Microsoft provides as part of their template but when I add a new controller called UserController with [RouteArea("Admin")] the other links will stop working such as Home/Contact, Home/About once I visit the Admin area (/Admin/User/Index) but if I manually type in the address bar I've created a new ASP.NET MVC 5 using Visual S