the name "model" doesnt exist in the current context error

Question

I upgrade my solution from 2013 to 2015 and v4.6 framework. I have only two projects in solution. when I  build my solution , it seems to build successfully but when I look at the error list, I am seeing erros on

@model and Html helpers.. etc.

It says The name "model" does not exist in the current context

The name "ViewBag" does not exist in the current context .

 

 

 

My application is MVC 4 version. Please help!