也许这有帮助

对我来说，删除位于C:\Users\YourNameHere的.nuget文件夹解决了这个问题。

在我的例子中，我只是重新启动docker并工作。

有些开发环境可能既不使用浏览器也不使用代理。

一种解决方案是从nugget(例如https://dotnet.myget.org/F/dotnet-core/api/v3/index.json)下载包到共享目录，然后执行以下操作:

dotnet add package Microsoft.AspNetCore.StaticFiles -s "shared drive:\index.json"

我希望这对你有用。  

I had the same error message while scaffolding Identity to my ASP.NET Core MVC project. Since my connection was not behind a proxy, removing/editing proxy configurations didn't make sense. And I didn't want to delete a file or uninstall PMC either. While looking around I realized a "Clear All Nuget Cache(s)" button on Tools --> Options --> NuGet Package Manager --> General. After pressing the button I had to wait for some time for the operation to complete. After that I tried to scaffold the Identity again but it didn't work. Then I decided to restart VS and voila :)

如果您得到此错误，但没有代理服务器，则可以转到

%userprofile%\AppData\Roaming\NuGet\NuGet.Config

并注释这行:

<config>
     <!-- Proxy settings -->
     <add key="http_proxy" value="host" />
     <add key="http_proxy.user" value="username" />
     <add key="http_proxy.password" value="encrypted_password" />
</config>

它为我工作，因为我得到了这个错误，但我没有代理服务器。

我在Visual Studio 2015上执行Install-Package Modernizr时遇到了类似的问题。我通过以下步骤解决了这个问题:

Download the package from its online source. Go to Tools/NuGet Package Manager/Package Manager Settings. Select Package Sources from the window. Add a new package source by clicking on the + sign. Enter a name and source location by clicking on ... (triple dot) sign. Make sure that only the package source that you've just added is checked. Uncheck all the other package sources. Go to Package Manager Console and type Install-Package Modernizr. Visual Studio 2015 installs the package automatically and creates Scripts and packages folders in your root folder.

我希望同样的解决方案在安装其他包时也能起作用。