nuget - 无法更新或安装包 : An item with the same key has already been added

Question

问题

在特定项目中，我无法更新或安装任何 NuGet 包。当我尝试使用 NuGet GUI 执行此操作时，它会执行一些操作，然后停止而什么也没说。当我尝试使用包管理器控制台执行此操作时，我得到以下输出:

PM> Update-Package –reinstall EntityFramework
Attempting to gather dependencies information for multiple packages with respect to project 'SmartCentre', targeting '.NETFramework,Version=v4.5.2'
Update-Package : An item with the same key has already been added.
At line:1 char:15
+ Update-Package <<<<  –reinstall EntityFramework
    + CategoryInfo          : NotSpecified: (:) [Update-Package], Exception
    + FullyQualifiedErrorId : NuGetCmdletUnhandledException,NuGet.PackageManagement.PowerShellCmdlets.UpdatePackageCommand

环境

Visual Studio Professional 2015 更新 1

NuGet 3.3.0.167

我试过的

删除 packages文件夹

重新启动 Visual Studio

重启电脑

Answer 1

原来是packages.config文件有几个不同版本的重复项:

<?xml version="1.0" encoding="utf-8"?>
<packages>
  <!-- ... -->
  <package id="Microsoft.AspNet.Web.Optimization" version="1.0.0" targetFramework="net40" />
  <package id="Microsoft.AspNet.Web.Optimization" version="1.1.2" targetFramework="net40" />
  <!-- ... -->
  <package id="Newtonsoft.Json" version="4.5.11" targetFramework="net40" />
  <package id="Newtonsoft.Json" version="5.0.8" targetFramework="net40" />
  <!-- ... -->
</packages>

一旦我删除了重复项，问题就会停止发生:

<?xml version="1.0" encoding="utf-8"?>
<packages>
  <!-- ... -->
  <package id="Microsoft.AspNet.Web.Optimization" version="1.1.2" targetFramework="net40" />
  <!-- ... -->
  <package id="Newtonsoft.Json" version="5.0.8" targetFramework="net40" />
  <!-- ... -->
</packages>