项目使用的 Nuget 包，比如 Microsoft.AspNetCore.App等的版本号要与 .NET Core 版本号（不是SDK版本号，后续说明）保持一致，否则编译或者运行的时候可能会出现一些稀奇古怪的错误。
二. 版本对照
二. 版本对照
1.查看所有安装的SDK
$ dotnet --list-sdks
1.0.0-preview2-003121 [/usr/local/share/dotnet/sdk]1.0.1 [/usr/local/share/dotnet/sdk]2.0.3 [/usr/local/share/dotnet/sdk]2.1.300 [/usr/local/share/dotnet/sdk]2.1.403 [/usr/local/share/dotnet/sdk]2.查看运行时
$ dotnet --list-runtimes
Microsoft.AspNetCore.All 2.1.0 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All]Microsoft.AspNetCore.All 2.1.5 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All]Microsoft.AspNetCore.App 2.1.0 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]Microsoft.AspNetCore.App 2.1.5 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]Microsoft.NETCore.App 1.0.0 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]Microsoft.NETCore.App 1.0.4 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]Microsoft.NETCore.App 1.1.1 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]Microsoft.NETCore.App 2.0.3 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]Microsoft.NETCore.App 2.1.0 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]Microsoft.NETCore.App 2.1.5 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]卸载 .NET Core Runtime and SDK
MAC上面，通过删除包含版本的目录，分开卸载SDKs 和 runtimes（SDK 和 runtime的目录，通过 dotnet --list-sdks 和 dotnet --list-runtimes 命令显示），例如删除 1.0.1 SDK 和 runtime，命令如下：
sudo rm -rf /usr/local/share/dotnet/sdk/1.0.1sudo rm -rf /usr/local/share/dotnet/shared/Microsoft.NETCore.App/1.0.1sudo rm -rf /usr/local/share/dotnet/shared/Microsoft.AspNetCore.App/1.0.1sudo rm -rf /usr/local/share/dotnet/host/fxr/1.0.1
从 .NET Core 2.1 开始, 使用package manager升级时，不再需要卸载 .NET Core SDK ，新版本安装成功会自动删除旧版本。
指定SDK版本
.NET Core 版本: .NET Core 项目默认使用最新版本的 .NET Core
SDK版本： 指定项目SDK版本，dotnet new global.json --sdk-version <SDK版本号>
