https://dotnet.microsoft.com/zh-cn/platform/dotnet-standard#versions
.NET Standard 版本
已对 .NET Standard 进行版本控制。每个新版本都添加了更多 API。当库是针对 .NET Standard 的某个版本生成时，它可以在任何 .NET 实现上运行，该版本实现 .NET Standard(或更高版本)。
Targeting a higher version of .NET Standard allows a library to use more APIs but means it can only be used on more recent versions of .NET. Targeting a lower version reduces the available APIs but means the library can run in more places.
