Predefined type 'System.Object' is not defined or imported .net 4.6

Question

I\'m using MVC 5 and .net 4.6 to create a web API that my mobile app can connect too.

Whenever I build the project I get hundreds of errors telling me that I need to add

Answer 1

In my case, below are the steps I followed;

1. I removed bin and obj and rebuild. (Didn't work)
2. Unloaded the project. (It resulted in "Assets file project.assets.json not found. Run a NuGet package restore")
3. I ran dotnet restore command via Visual Studio 2017 >> Tools >> NuGet Package Manager >> Package Manager Console.
4. Rebuild solution. (Problem solved)

Answer 2

I have the same problem. I spent 2 day to resolve this problem. I try reinstall visual, clear cache visual, uninstall visual or setup windows 10 again => but not success.

You can try follow step, it success for me

1. Close visual
2. Delete packages folder in solution folder
3. Open visual and rebuild solution

Good luck

Answer 3

Remove bin and obj and rebuild.

Answer 4

In my case, I had a project that was still set to build against a beta version of dnx. Changing it to build against the version I was using in the other projects fixed it.

Answer 5

I just opened Visual Studio "As Administrator" and it worked!

Answer 6

Took almost 2 days to fix. Tried VS Uninstall\re-install several times but did not work.

What finally worked for me...

Ran VS Installer repair. Due to errors, I had to manually uninstall all instances MS .NET Core SDK - 2.1xxx

Ran VS Installer repair. No errors. Remove bin and obj and rebuild.

Ran dotnet restore command on Package manager console and problem solved.