运行所选代码生成器时出错 程序包还原失败。正在回滚

nuget包自动下载失败。既然自动下载失败那就手机下载

  <ItemGroup>
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="3.1.21" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="3.1.21">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="3.1.5" />
  </ItemGroup>

其实主要是Microsoft.VisualStudio.Web.CodeGeneration.Design这个库，还有就是对应.net core版本的版本问题。

比如这里就是对应的3.1.21