为什么 Entity Framework Core 迁移需要 .NET Core 2.x？

Question

In my .NET5.0 project the PostgreSQL Nuget package is installed ( Npgsql.EntityFrameworkCore.PostgrSQL (5.0.2) ) and its dependency of EF Core ( Microsoft.EntityFrameworkCore (5.0.2) ).

I'm trying to create a migration using this command:

dotnet ef migrations add InitialCreate

However, the migration fails because I'm requested to install .NET Core 2.0.0 - following the recommended download link I'm told that it's no longer available and that I would likely want to use 5.0. How the heck can I run the migration?

This is what the output looks:

Build started...
Build succeeded.
It was not possible to find any compatible framework version
The framework 'Microsoft.NETCore.App', version '2.0.0' was not found.
  - The following frameworks were found:
      3.1.11 at [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
      3.1.12 at [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
      3.1.13 at [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
      5.0.3 at [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
      5.0.4 at [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

You can resolve the problem by installing the specified framework and/or SDK.

The specified framework can be found at:
  - https://aka.ms/dotnet-core-applaunch?framework=Microsoft.NETCore.App&framework_version=2.0.0&arch=x64&rid=osx.11.0-x64

Answer 1

Make sure you have <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="5.0.5" /> in your csproj. Also try updating the dotnet-ef tool: dotnet tool update --global dotnet-ef .

I performed these actions and the issue went away.

Answer 2

This can occur if you run the command in a class library. You can point to the startup-project when running the command:

dotnet ef migrations add InitialCreate --startup-project <PathToProject>