'在 Package 管理器控制台中找不到 Microsoft.NETCore.App 2.0.0

Question

I recently upgraded my .NET projects from .NET 5.0 to .NET 6.0.

When I attempt to add a migration in Package Manager Console, I get the following error.

It was not possible to find any compatible framework version
The framework 'Microsoft.NETCore.App', version '2.0.0' (x64) was not found.
  - The following frameworks were found:
      5.0.12 at [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
      6.0.0 at [C:\Program Files\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=win10-x64

I'm confused by this. Why is it looking for version 2.0.0 of Microsoft.NETCore.App ? Is that an older version? And why would it be missing now that I've updated my projects to .NET 6.0?

I looked in my project but don't see any reference to this package. Can anyone help me understand what is wrong?

Update

Here is the project file for my main application.

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
    <SatelliteResourceLanguages>en</SatelliteResourceLanguages>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="6.0.0" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="6.0.0">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="6.0.0" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="6.0.0">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="6.0.0" />
    <PackageReference Include="Swashbuckle.AspNetCore" Version="6.2.3" />
  </ItemGroup>

  <ItemGroup>
    <ProjectReference Include="..\TTRailtraxBusinessLayer\TTRailtraxBusinessLayer.csproj" />
    <ProjectReference Include="..\TTRailtraxEntities\TTRailtraxEntities.csproj" />
  </ItemGroup>

  <ItemGroup>
    <Folder Include="Attributes\" />
  </ItemGroup>

</Project>

And here is the project file for the library project that contains my entities.

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="6.0.0" />
  </ItemGroup>

  <ItemGroup>
    <ProjectReference Include="..\RailtraxCore\RailtraxCore.csproj" />
  </ItemGroup>

</Project>

As you can see, there are other library projects being used as well.

Answer 1

Well, Entity Framework's tooling for Powershell has a semantic to pass parameters into EF tools. It passes both the default project and the startup project but for multiple startup projects, it uses the default project as a fallback project. EF tools requires a configured DbContext (associated with a provider and connection string) this is the startup project that consumes the DbContext and configures it. And a migration assembly that locates the migrations and that is usually the project that contains DbContext. So generally when I add migrations with PMC I set the startup project to an application and set the default project in PMC to the DbContext project.

Here is the Powershell module if you want to dig deeper.

Answer 2

Try changing project framework to the ones that are found ie 3.1 or 5.0: Right click on project -> Properties -> Application -> Target framework