My problem is very similar to this problem, except mine is in a sub-Area (right click, Create Area)
The name 'ViewBag' does not exist in the current context
I ran the upgrade tool and it did discover the web.config in the area, but I still get the error. My layout page is very simple:
<!DOCTYPE html>
<html>
<head>
    <title>@ViewBag.Title</title>
</head>
<body>
    <div>
        @RenderBody()
    </div>
</body>
</html>
And my content page looks like this near the top:
@model IEnumerable<ProjectName.Models.OrderViewModel>
@{
    ViewBag.Title = "Index";
    Layout = "~/Areas/Admin/_AdminLayoutPage.cshtml";
}
<h2>Index</h2>
 
     
    
 
     
    