I created a new MVC project in Visual Studio 2017. I wanted to add an EDMX file (I will be doing database-first) so right clicked on the project and selected Add|New Item.
I had a similar issue today after i updated my VS to the latest 2017 version. I tried to open an .edmx file in VS2017 and it didn't show the designer view. So i realised i forgot to select Entity Framework tools during the installation: