我正在尝试使用[电子邮件受保护]。为了在这一点上做到这一点，我已经有了：
- 安装了 Visual Studio 2019 预览版
- 安装了.NET Core 3.1运行时
- 安装了.NET Core 3.1 SDK
现在我仍然无法运行命令dotnet ef migrations add xxx。它说我必须更新 dotnet 工具。因此，我在管理员 powershell 中运行以下命令：
PS C:\WINDOWS\system32> dotnet tool update --global dotnet-ef
Tool 'dotnet-ef' was reinstalled with the latest stable version (version '3.0.0')
好的，不包括预览版本。所以我尝试明确指定版本：
PS C:\WINDOWS\system32> dotnet tool update --global dotnet-ef --version="3.1.0-preview1.19506.2"
error NU1202: Package dotnet-ef 3.1.0-preview1.19506.2 is not compatible with netcoreapp3.1 (.NETCoreApp,Version=v3.1) / any. Package dotnet-ef 3.1.0-preview1.19506.2 supports: netcoreapp3.1 (.NETCoreApp,Version=v3.1)
Tool 'dotnet-ef' failed to update due to the following:
The tool package could not be restored.
Tool 'dotnet-ef' failed to install. This failure may have been caused by:
* You are attempting to install a preview release and did not use the --version option to specify the version.
* A package by this name was found, but it was not a .NET Core tool.
* The required NuGet feed cannot be accessed, perhaps because of an Internet connection problem.
* You mistyped the name of the tool.
For more reasons, including package naming enforcement, visit https://aka.ms/failure-installing-tool
现在它说 .NET Core 3.1 工具与 .NET Core 3.1 运行时不兼容。
但是，如果我进行简单的版本检查：
PS C:\WINDOWS\system32> dotnet --version
3.1.100-preview1-014459
PS C:\WINDOWS\system32> dotnet ef --version
Entity Framework Core .NET Command-line Tools
3.0.0
我可以看到 EntityFrameworkCore.Tools 仍然是版本 3.0.0 而不是 3.1.0（我的项目中安装了哪个工具版本）。
我是否还缺少某些东西或者这是一个错误？
