System could not be found Visual Studio 2017 ASP.NET Core project

Question

I\'ve installed the newly released version of Visual Studio 2017 and started a fresh ASP.NET Core project targeting .NET Core.

Out of the box, I\'m getting the

Answer 1

Find the broken project and right click, Unload, right click, Re-load. Fastest fix for me.

If you get the problem while using the CLI, try doing nuget restore instead of dotnet restore as that sometimes pulls down packages that the dotnet CLI seems to miss.

Answer 2

I had the same issue in my Visual studio 2017 .Net Core application. I closed the Visual studio and re-open fixed everything.

Answer 3

Simply opening the NuGet package manager and then the Visual Studio settings related to it - without changing anything - merely looking around, and when I closed out, the problem was gone.

This seems to be an intermittent issue that can come and go for no obvious reason.

Answer 4

I had the same issue, the solution for me was to clear the NuGet cache. Tools > NuGet Package Manager > Package Manager Settings > Clear All NuGet Cache(s)

Answer 5

Had the same problem. Uninstalled Application Insights from my projects using the nuget package manager. I'm not looking at that yet, I just wanted core and unit tests. Problem solved.

Answer 6

I was facing the same issue when I created a new project (.net Core 2.2) in VS2019.In my case there was an Azure package which was creating the problem.I uninstalled it and the project started working fine. Run mentioned below command to uninstall the package.

Uninstall-Package Microsoft.VisualStudio.Azure.Containers.Tools.Targets -Version 1.7.10