installing nuget package "same key has already been added."

Question

i am trying to install Microsoft.Bcl.Build 1.0.14

nuget returns

Installing 'Microsoft.Bcl.Build 1.0.14'. Successfully installed 'Microsoft.Bcl.Build 1.0.14'. Adding 'Microsoft.Bcl.Build 1.0.14' to LeadTracker.Calendar. Uninstalling 'Microsoft.Bcl.Build 1.0.14'. Successfully uninstalled 'Microsoft.Bcl.Build 1.0.14'. Install failed. Rolling back... An item with the same key has already been added.

This also happens with json.net and other packages.

I can add nancy and topshelf but not json.net and bcl.

I have tried it in VS2012 and 2013. I have also tried uninstalling nuget and reinstalling. I have also tried adding the nuget to an empty class library and an empty console app. The same error is always returned.

This also happens with json.net and other packages.

I have also tried with no packages file

Any ideas most appreciated.

Here is the command and stacktrace

PM> Install-Package Microsoft.Bcl.Build Installing 'Microsoft.Bcl.Build 1.0.14'. You are downloading Microsoft.Bcl.Build from Microsoft, the license agreement to which is available at http://go.microsoft.com/fwlink/?LinkId=329770. Check the package for additional dependencies, which may come with their own license agreement(s). Your use of the package and dependencies constitutes your acceptance of their license agreements. If you do not accept the license agreement(s), then delete the relevant components from your device. Successfully installed 'Microsoft.Bcl.Build 1.0.14'. Adding 'Microsoft.Bcl.Build 1.0.14' to GoogleCalendarIntegration. Uninstalling 'Microsoft.Bcl.Build 1.0.14'. Successfully uninstalled 'Microsoft.Bcl.Build 1.0.14'. Install failed. Rolling back... Install-Package : An item with the same key has already been added. At line:1 char:1
+ Install-Package Microsoft.Bcl.Build
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Install-Package], ArgumentException
    + FullyQualifiedErrorId : NuGetCmdletUnhandledException,NuGet.PowerShell.Commands.InstallPac     kageCommand   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 System.Collections.ObjectModel.KeyedCollection`2.AddKey(TKey key, TItem item)    at System.Collections.ObjectModel.KeyedCollection`2.InsertItem(Int32 index, TItem item)    at System.Collections.ObjectModel.Collection`1.Add(T item)    at NuGet.CollectionExtensions.AddRange[T](ICollection`1 collection, IEnumerable`1 items)    at NuGet.NetPortableProfileTable.BuildPortableProfileCollection()    at NuGet.NetPortableProfileTable.get_Profiles()    at NuGet.NetPortableProfileTable.GetProfile(String profileName)    at NuGet.NetPortableProfile.Parse(String profileValue, Boolean treatOptionalFrameworksAsSuppor tedFrameworks)    at NuGet.VersionUtility.IsPortableLibraryCompatible(FrameworkName projectFrameworkName, Framew orkName packageTargetFrameworkName)    at NuGet.VersionUtility.IsCompatible(FrameworkName projectFrameworkName, FrameworkName package TargetFrameworkName)    at NuGet.VersionUtility.<>c__DisplayClass8`1.<TryGetCompatibleItems>b__15(IGrouping`2 g)    at System.Linq.Enumerable.WhereListIterator`1.MoveNext()    at System.Linq.Buffer`1..ctor(IEnumerable`1 source)    at System.Linq.OrderedEnumerable`1.<GetEnumerator>d__0.MoveNext()    at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source)   at NuGet.VersionUtility.TryGetCompatibleItems[T](FrameworkName projectFramework, IEnumerable`1  items, IEnumerable`1& compatibleItems)    at NuGet.ProjectSystemExtensions.GetCompatibleItemsCore[T](IProjectSystem projectSystem, IEnum erable`1 items)    at NuGet.ProjectManager.ExtractPackageFilesToProject(IPackage package)    at NuGet.ProjectManager.AddPackageReferenceToProject(IPackage package) at NuGet.ProjectManager.Execute(PackageOperation operation)    at NuGet.ProjectManager.Execute(IPackage package, IPackageOperationResolver resolver)    at NuGet.ProjectManager.AddPackageReference(IPackage package, Boolean ignoreDependencies, Bool ean allowPrereleaseVersions)    at NuGet.VisualStudio.VsPackageManager.<>c__DisplayClass83.<AddPackageReference>b__85() at NuGet.VisualStudio.VsPackageManager.RunProjectAction(IProjectManager projectManager, Action  action)    at NuGet.VisualStudio.VsPackageManager.AddPackageReference(IProjectManager projectManager, IPa ckage package, Boolean ignoreDependencies, Boolean allowPrereleaseVersions)    at NuGet.VisualStudio.VsPackageManager.<>c__DisplayClass3.<InstallPackage>b__7() at NuGet.VisualStudio.VsPackageManager.RunSolutionAction(Action action)    at NuGet.VisualStudio.VsPackageManager.InstallPackage(IProjectManager projectManager, String p ackageId, SemanticVersion version, Boolean ignoreDependencies, Boolean allowPrereleaseVersions, B oolean skipAssemblyReferences, ILogger logger)    at NuGet.VisualStudio.VsPackageManager.InstallPackage(IProjectManager projectManager, String p ackageId, SemanticVersion version, Boolean ignoreDependencies, Boolean allowPrereleaseVersions, I Logger logger)  at NuGet.PowerShell.Commands.InstallPackageCommand.InstallPackage(IVsPackageManager packageMan ager)    at NuGet.PowerShell.Commands.InstallPackageCommand.ProcessRecordCore()    at NuGet.PowerShell.Commands.NuGetBaseCommand.ProcessRecord() PM>

Answer 1

Check your packages.config Inside there, check for the packages you are trying to install. Maybe some reference are already there and this avoid that you can install the new ones.

If you find there the references, delete the reference from the packages.config and try to install again the package.

It happened to me sometimes that inside packages.config are some old reference that still left there even after removing the package from the Nuget Package Manager.

If not, you can delete the entire packages.config, then if you have the option to let Nuget download the packages, when you build your solution, the packages will be downloaded again.

I hope this helps