Visual Studio stopped supporting my projects

Question

I have Visual Studio 2013 Ultimate. Today when I opened it, it didn't load any of my solution's projects. Error message:

Unsupported
This version of Visual Studio is unable to open the following projects. The project types may not be installed or this version of Visual Studio may not support them. 
For more information on enabling these project types or otherwise migrating your assets, please see the details in the "Migration Report" displayed after clicking OK.
     - ETL_<Project name>, "<Project path></Project>.csproj"


Non-functional changes required
Visual Studio will automatically make non-functional changes to the following projects in order to enable them to open in Visual Studio 2013, Visual Studio 2012, and Visual Studio 2010 SP1. Project behavior will not be impacted.
     - <Project name></Project>, "<Project path></Project>.sln"

These projects are of types Class Library and Console Application. If I try to create a new project, these types are listed, but when I create it I get message <Project path> cannot be opened because its project type (.csproj is not supported by this version of the application. To open it, please use a version that supports this type of project. .

So, Visual Studio is telling me it doesn't support a project it just created?! GJ M$!!

Answer 1

Unfortunately I was unable to solve this. I ended up uninstalling VS Ultimate. Now I use VS Express for Desktop, and it works with my old projects.

My assumption is that something on Windows broke some part of VS. I should have tried to uninstall and reinstall it but didn't have the opportunity.

Answer 2

I have the same thing in a Hyper-V VM. After repair did not work, I deinstalled and reinstalled VS 2017. Same thing. In the host I can still open the same project with VS, so it is not the project, but the VS install that has a problem.

It puts this in the migration log: src\\DTOWEB\\project.json: Failed to migrate XProj project DTOWEB. Could not find project.json at C:\\DTOWeb\\DTOWEB7\\src\\DTOWEB\\project.json.

I have a second VM that is x86 iso x64, and it can open the project without problems. So again, my conclusion is there is nothing wrong with the project.