Visual Studio and PMC restore/update fails when multiple packages.config projects in the solution share the same name (An item with the same key has already been added)

[nkolev92]

#13456

PM> Update-Package -reinstall
Update-Package : An item with the same key has already been added.
At line:1 char:1
+ Update-Package -reinstall
+ ~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Update-Package], ArgumentException
    + FullyQualifiedErrorId : NuGetCmdletUnhandledException,NuGet.PackageManagement.PowerShellCmdlets.UpdatePackageCommand
 
PM> $error[0].Exception.StackTrace
   at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
   at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   at NuGet.PackageManagement.PackageRestoreManager.<GetRestoreAuditProperties>d__31.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at NuGet.PackageManagement.PackageRestoreManager.<RestoreMissingPackagesAsync>d__35.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at NuGet.PackageManagement.PowerShellCmdlets.NuGetPowerShellBaseCommand.<CheckMissingPackagesAsync>d__64.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at NuGet.PackageManagement.PowerShellCmdlets.PackageActionBaseCommand.<<Preprocess>b__39_0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.Threading.JoinableTask.CompleteOnCurrentThread()
   at NuGet.PackageManagement.PowerShellCmdlets.PackageActionBaseCommand.Preprocess()
   at NuGet.PackageManagement.PowerShellCmdlets.UpdatePackageCommand.Preprocess()
   at NuGet.PackageManagement.PowerShellCmdlets.UpdatePackageCommand.ProcessRecordCore()
   at NuGet.PackageManagement.PowerShellCmdlets.NuGetPowerShellBaseCommand.ProcessRecord()

[Nevcairiel]

I've attached a very simple example to trigger the issue, the solution contains two projects with the same name, organized into folders, which allows to actually do this without getting errors from VS.

Just trying to build the project not in the sub-folder should grab NuGet dependencies, but it fails with the aforementioned error.

NuGetTestProject.zip