Question: package restore failed rolling back package change for ' my project' in vs 2017 .net MVC core project while updating packages

Answer: 
I have the same problem. Created a new app ASP.Net Core(.Net Framework). And wanted to add the library, but faced the error. When trying to update the same problem.
[![enter image description here](https://i.stack.imgur.com/RlxwL.png)](https://i.stack.imgur.com/RlxwL.png)[![enter image description here](https://i.stack.imgur.com/qc9Ai.png)](https://i.stack.imgur.com/qc9Ai.png)

**FIXED**

The solution was simple. When creating the project I chose ASP.NET CORE v 1. After rebuilding the project ASP.NET CORE v 2, it worked.

[![enter image description here](https://i.stack.imgur.com/J8yGn.png)](https://i.stack.imgur.com/J8yGn.png)
Try to delete the "packages" folder in your solution and all the projects and colse-reopen Visual Studio