ASP.NET MVC模糊类型错误 - 'System.Web.Mvc.ViewMasterPage'不明确

I created an ASP.NET MVC 2.0 Application. It ran fine at first test and I made some minor edits to the views. I then wanted to add a new controller so I had to compile the app. After I did anytime I run it I get the following error:I created an ASP.NET MVC 2.0 Application. It ra