NuGet Package Manager - Project 'Default' is not found. - Visual Studio 2017

Question

I am using Visual Studio 2017 Community and I am trying to build a solution for a project I just started working on.

Whenever I try to build the solution file, I get these errors:

C:\Projects\UnitTests\UnitTests.csproj(91,5): error : This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is ..\packages\MSTest.TestAdapter.1.1.18\build\net45\MSTest.TestAdapter.props.
C:\Projects\WebAPI\WebAPI.csproj(469,5): error : This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is ..\packages\Microsoft.Net.Compilers.2.1.0\build\Microsoft.Net.Compilers.props.
C:\Projects\APITester\APITester.csproj(316,5): error : This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is ..\packages\Microsoft.Net.Compilers.2.6.1\build\Microsoft.Net.Compilers.props.
C:\Projects\Admin\Admin.csproj(391,5): error : This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is ..\packages\Microsoft.Net.Compilers.2.6.1\build\Microsoft.Net.Compilers.props.

If I try to run

Update-Package --reinstall

or

Install-Package Microsoft.Net.Compilers -Version 2.6.1

I get the following errors:

Install-Package : Project 'Default' is not found.
At line:1 char:1
+ Install-Package Microsoft.Net.Compilers -Version 2.6.1
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (Default:String) [Install-Package], ItemNotFoundException
    + FullyQualifiedErrorId : NuGetProjectNotFound,NuGet.PackageManagement.PowerShellCmdlets.InstallPackageCommand


Update-Package : Project 'Default' is not found.
At line:1 char:1
+ Update-Package --reinstall
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (Default:String) [Update-Package], ItemNotFoundException
    + FullyQualifiedErrorId : NuGetProjectNotFound,NuGet.PackageManagement.PowerShellCmdlets.UpdatePackageCommand

Answer 1

Open the solution for those projects as that will automatically set the default project. Then you will be able to install those nuget packages.