C# 无法解析'；微软.NETCore.App（>；=2.1.0）和#x27；对于'；。NETCoreApp，版本=v2.1'；

我正在尝试使用dotnet restore解析nugget软件包，但遇到以下错误：

无法解析“.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>

netcoreapp2.1
$（MSBuildThisFileDirectory）Web.config
$（MSBuildThisFileDirectory）Web.$（配置）.config
$（PublishDir）Web.config

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我已经安装了dotnet-sdk-2.1.300-rc1-008673-win-x64，我正在使用Visual Studio 2017 v15.2，问题是Visual Studio版本

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解决方案是创建指向dotnet\sdk{{{version}}\sdk的MSBuildSdksPath环境变量，就像下面的链接一样，我必须在位于 C:\Users\userid\AppData\Roaming\NuGet以解决上述问题

<configuration>
<packageSources>
    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" protocolVersion="3" />
    <add key="nuget.org" value="https://www.nuget.org/api/v2/" />   
  </packageSources>
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