MvcScaffolding NuGet installation: "An item with the same key has already been added"

Question

I'm getting an error when installing MvcScaffolding through NuGet. Has anyone got any suggestions for how to fix the problem?

PM> install-Package MvcScaffolding -Verbose
Dependency 'T4Scaffolding (≥ 1.0.0)' already installed.
Dependency 'EntityFramework (≥ 4.1.10311.0)' already installed.
Added file 'InstallationDummyFile.txt' to folder 'MvcScaffolding.1.0.0\content'.
Added file 'Action.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\Action'.
Added file 'Action.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\Action'.
Added file 'ActionPost.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\Action'.
Added file 'ActionPost.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\Action'.
Added file 'MvcScaffolding.Action.ps1' to folder 'MvcScaffolding.1.0.0\tools\Action'.
Added file 'ViewModel.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\Action'.
Added file 'ViewModel.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\Action'.
Added file 'MvcScaffolding.ActionUnitTest.ps1' to folder 'MvcScaffolding.1.0.0\tools\ActionUnitTest'.
Added file 'TestClass.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\ActionUnitTest'.
Added file 'TestClass.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\ActionUnitTest'.
Added file 'TestMethod.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\ActionUnitTest'.
Added file 'TestMethod.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\ActionUnitTest'.
Added file 'MvcScaffolding.ActionWithUnitTest.ps1' to folder 'MvcScaffolding.1.0.0\tools\ActionWithUnitTest'.
Added file 'Create.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\AspxView'.
Added file 'Create.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\AspxView'.
Added file 'CreateOrEdit.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\AspxView'.
Added file 'CreateOrEdit.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\AspxView'.
Added file 'Delete.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\AspxView'.
Added file 'Delete.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\AspxView'.
Added file 'Details.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\AspxView'.
Added file 'Details.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\AspxView'.
Added file 'Edit.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\AspxView'.
Added file 'Edit.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\AspxView'.
Added file 'Empty.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\AspxView'.
Added file 'Empty.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\AspxView'.
Added file 'Index.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\AspxView'.
Added file 'Index.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\AspxView'.
Added file 'MvcScaffolding.AspxView.ps1' to folder 'MvcScaffolding.1.0.0\tools\AspxView'.
Added file 'ControllerWithContext.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\Controller'.
Added file 'ControllerWithContext.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\Controller'.
Added file 'ControllerWithRepository.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\Controller'.
Added file 'ControllerWithRepository.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\Controller'.
Added file 'MvcScaffolding.Controller.ps1' to folder 'MvcScaffolding.1.0.0\tools\Controller'.
Added file 'MvcScaffolding.ControllerWithRepository.ps1' to folder 'MvcScaffolding.1.0.0\tools\Controller'.
Added file 'init.ps1' to folder 'MvcScaffolding.1.0.0\tools'.
Added file 'install.ps1' to folder 'MvcScaffolding.1.0.0\tools'.
Added file 'Create.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\RazorView'.
Added file 'Create.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\RazorView'.
Added file 'Delete.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\RazorView'.
Added file 'Delete.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\RazorView'.
Added file 'Details.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\RazorView'.
Added file 'Details.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\RazorView'.
Added file 'Edit.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\RazorView'.
Added file 'Edit.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\RazorView'.
Added file 'Empty.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\RazorView'.
Added file 'Empty.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\RazorView'.
Added file 'Index.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\RazorView'.
Added file 'Index.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\RazorView'.
Added file 'MvcScaffolding.RazorView.ps1' to folder 'MvcScaffolding.1.0.0\tools\RazorView'.
Added file '_CreateOrEdit.cs.t4' to folder 'MvcScaffolding.1.0.0\tools\RazorView'.
Added file '_CreateOrEdit.vb.t4' to folder 'MvcScaffolding.1.0.0\tools\RazorView'.
Added file 'registerWithMvcTooling.ps1' to folder 'MvcScaffolding.1.0.0\tools'.
Added file 'MvcScaffolding.Views.ps1' to folder 'MvcScaffolding.1.0.0\tools\Views'.
Added file 'MvcScaffolding.1.0.0.nupkg' to folder 'MvcScaffolding.1.0.0'.
Successfully installed 'MvcScaffolding 1.0.0'.
Executing script file 'C:\MyProject\packages\MvcScaffolding.1.0.0\tools\init.ps1'.
Added file 'InstallationDummyFile.txt'.
Added file 'InstallationDummyFile.txt' to project 'ReinsuranceManagementWebUI'
Added file 'packages.config'.
Added file 'packages.config' to project 'ReinsuranceManagementWebUI'
Successfully added 'MvcScaffolding 1.0.0' to ReinsuranceManagementWebUI.
Executing script file 'C:\MyProject\packages\MvcScaffolding.1.0.0\tools\install.ps1'.
Get-ProjectItem : An item with the same key has already been added.
At C:\MyProject\packages\MvcScaffolding.1.0.0\tools\install.ps1:22 char:16
+ Get-ProjectItem <<<<  "InstallationDummyFile.txt" -Project $projectName | %{ $_.Delete() }
    + CategoryInfo          : NotSpecified: (:) [Get-ProjectItem], ArgumentException
    + FullyQualifiedErrorId : T4Scaffolding.Cmdlets.GetProjectItemCmdlet

Set-DefaultScaffolder : An item with the same key has already been added.
At C:\MyProject\packages\MvcScaffolding.1.0.0\tools\install.ps1:24 char:22
+ Set-DefaultScaffolder <<<<  -Name Controller -Scaffolder MvcScaffolding.Controller -SolutionWide -DoNotOverwriteExistingSetting
    + CategoryInfo          : NotSpecified: (:) [Set-DefaultScaffolder], ArgumentException
    + FullyQualifiedErrorId : T4Scaffolding.Cmdlets.SetDefaultScaffolderCmdlet

Set-DefaultScaffolder : An item with the same key has already been added.
At C:\MyProject\packages\MvcScaffolding.1.0.0\tools\install.ps1:25 char:22
+ Set-DefaultScaffolder <<<<  -Name Views -Scaffolder MvcScaffolding.Views -SolutionWide -DoNotOverwriteExistingSetting
    + CategoryInfo          : NotSpecified: (:) [Set-DefaultScaffolder], ArgumentException
    + FullyQualifiedErrorId : T4Scaffolding.Cmdlets.SetDefaultScaffolderCmdlet

Set-DefaultScaffolder : An item with the same key has already been added.
At C:\MyProject\packages\MvcScaffolding.1.0.0\tools\install.ps1:26 char:22
+ Set-DefaultScaffolder <<<<  -Name Action -Scaffolder MvcScaffolding.Action -SolutionWide -DoNotOverwriteExistingSetting
    + CategoryInfo          : NotSpecified: (:) [Set-DefaultScaffolder], ArgumentException
    + FullyQualifiedErrorId : T4Scaffolding.Cmdlets.SetDefaultScaffolderCmdlet

Set-DefaultScaffolder : An item with the same key has already been added.
At C:\MyProject\packages\MvcScaffolding.1.0.0\tools\install.ps1:27 char:22
+ Set-DefaultScaffolder <<<<  -Name UnitTest -Scaffolder MvcScaffolding.ActionUnitTest -SolutionWide -DoNotOverwriteExistingSetting
    + CategoryInfo          : NotSpecified: (:) [Set-DefaultScaffolder], ArgumentException
    + FullyQualifiedErrorId : T4Scaffolding.Cmdlets.SetDefaultScaffolderCmdlet

Set-DefaultScaffolder : An item with the same key has already been added.
At C:\MyProject\packages\MvcScaffolding.1.0.0\tools\install.ps1:31 char:22
+ Set-DefaultScaffolder <<<<  -Name View -Scaffolder $viewScaffolder -SolutionWide -DoNotOverwriteExistingSetting
    + CategoryInfo          : NotSpecified: (:) [Set-DefaultScaffolder], ArgumentException
    + FullyQualifiedErrorId : T4Scaffolding.Cmdlets.SetDefaultScaffolderCmdlet

I've tried uninstalling the re-installing using this command:

Uninstall-Package MvcScaffolding -RemoveDependencies

Answer 1

As mentioned in the comments on the original question, I believe this is a bug in MVC Scaffolding, see: http://mvcscaffolding.codeplex.com/workitem/27

Answer 2

I had problems with this error as well. What worked for me was to uninstall MvcScaffolding and each of its dependencies with a separate command for each uninstall as in 'Uninstall-Package T4Scaffolding'. I also deleted their associated files and folders from my drive and source control. Then, I re-installed and all was fine. That deletion of the files seemed to be key.