ASP.NET MVC错误：此处不允许页面，因为它不扩展类'System.Web.Page'

I have a new ASP.NET MVC project (my first), and I had been running fine with 1 controller, view, and model. After I added a new controller and view, my first view started throwing this error message when I try to run the project:I have a new ASP.NET MVC project (my first), an