无法解析“.NETCoreApp,Version=v2.1”

Question

我正在尝试使用 dotnet restore 解决 nugget 包，但出现此错误： Unable to resolve 'Microsoft.NETCore.App (>= 2.1.0)' for '.NETCoreApp,Version=v2.1'这是我的 .csproj 文件<Project Sdk="Microsoft.NET.Sdk.Web">  <PropertyGroup>    <TargetFramework>netcoreapp2.1</TargetFramework>  </PropertyGroup>  <ItemGroup>    <PackageReference Include="Autofac" Version="4.5.0" />    <PackageReference Include="Autofac.Extensions.DependencyInjection" Version="4.1.0" />    <PackageReference Include="Autofac.Extras.Moq" Version="4.2.0" />    <PackageReference Include="BCrypt.Net-Core" Version="1.4.0" />    <PackageReference Include="Easy.MessageHub" Version="3.2.1" />    <PackageReference Include="hangfire" Version="1.6.17" />    <PackageReference Include="Hangfire.MemoryStorage" Version="1.5.2" />    <PackageReference Include="Microsoft.AspNetCore.App" Version="2.1.0-rc1-final" />    <PackageReference Include="Microsoft.AspNetCore.Mvc" Version="2.1.0-rc1-final" />    <PackageReference Include="Microsoft.Extensions.Configuration" Version="2.1.0-rc1-final" />    <PackageReference Include="MongoDB.Driver" Version="2.4.4" />    <PackageReference Include="Swashbuckle.AspNetCore" Version="1.1.0" />    <PackageReference Include="System.Runtime.Extensions" Version="4.3.0" />  </ItemGroup>  <Target Name="ApplyXdtConfigTransform" BeforeTargets="_TransformWebConfig">    <PropertyGroup>      <_SourceWebConfig>$(MSBuildThisFileDirectory)Web.config</_SourceWebConfig>      <_XdtTransform>$(MSBuildThisFileDirectory)Web.$(Configuration).config</_XdtTransform>      <_TargetWebConfig>$(PublishDir)Web.config</_TargetWebConfig>    </PropertyGroup>    <Exec Command="dotnet transform-xdt --xml &quot;$(_SourceWebConfig)&quot; --transform &quot;$(_XdtTransform)&quot; --output &quot;$(_TargetWebConfig)&quot;" Condition="Exists('$(_XdtTransform)')" />  </Target></Project>我已经安装了 dotnet-sdk-2.1.300-rc1-008673-win-x64 并且我使用的是 Visual Studio 2017 v15.2