I have a very old Asp.NET mvc app, written about 3 years ago and unchanged since then. It uses KendoUI for user interface, and is built with KendoUI MVC helpers.
At that time (when I made it), all worked just fine.
Recently I had to make some enhancements to it, so I had to update it to latest KendoUI version.
After various minor adjustments, I managed to make it work, be able to build it. It also works just fine at runtime.
However I have a problem in design mode I don't know where it comes from, which makes it very hard to do any enhancements.
Specifically, in my views and partial views, a lot of elements are underlined with red and reported as error (see below)
Hovering mouse over any of them, like over HiddenFor extension method, gives a error message in popup as
HtmlHelper does not contain a definition for 'HiddenFor'
and no extension method 'HiddenFor' accepting a first argument of type
HtmlHelper could be found (are you missing a using directive or an assembly reference)
Also, even the model declaration is not recognized
I use VS 2015, and I have the correct reference to
