Does Visual Studio 2015 include .edmx support?
I have a project that includes an .edmx data model and double-clicking it in VS2015 just opens the XML editor.
There's no DbContext generator option in the file->new dialog.
During setup of VS2015, go to the advanced options and select Web or Database Development tools. Now the Installers install the EF tools (Designer + templates). If you have VS already installed, to the Programs & features in control panel and modify the currently installed VS2015.
You have to select the Microsoft SQL Server Data Tools in the VS2015 setup to get this editor back.
NOTE: You can modify the current installation via Program And Features as magicandre1981 has already suggested.
来源：https://stackoverflow.com/questions/32212919/does-visual-studio-2015-include-edmx-support