VS2019 错误说项目在定位 netcoreapp2.2 时定位到“netcoreapp3.1”

Question

I have a multi-project solution that was working fine in VS2017, I've installed VS2019 and on compile I receive five error messages:

Four of the format: This version of Microsoft.AspNetCore.App is only compatible with netcoreapp2.2 taret framework. Please target netcoreapp2.2 or chose a version of Microsoft.AspNetCore.app compatible with netcoreapp3.1

And one of the format: Project '..\\project-path\\project.csproj' targets 'netcoreapp3.1;. It cannot be reference by a project that targets '.NETCoreApp,Version=v2.2'

Additionally if you look at the projects referenced in the error messages the Dependencies, Packages, SDK all have the yellow warning symbol on them (hover and right-click don't seem to provide additional details)

I've tried cleans, delete bin and obj folders, rebuilds, checking SDK versions, but no luck

I can confirm I have a global.json with the SDK version (2.2.103) and that when in any of these projects directories and I run 'dotnet --verson' I get back 2.2.103

What is happening here? What / where is it picking up netcoreapp3.1 from and how do I resolve these errors?

Update: CSPROJ Details

  <PropertyGroup>
    <TargetFramework>netcoreapp2.2</TargetFramework>
    <LangVersion>7.3</LangVersion>
  </PropertyGroup>



 <ItemGroup>
    <None Include="appsettings.json" CopyToOutputDirectory="Always" />
    <None Include="favicon.ico" CopyToOutputDirectory="Always" />
    <None Include="appDevLocalOverride.json" />
    <PackageReference Include="Lamar.Microsoft.DependencyInjection" Version="3.1.0" />
    <PackageReference Include="Microsoft.ApplicationInsights.AspNetCore" Version="2.8.1" />
    <PackageReference Include="Microsoft.AspNetCore.App" />
    <PackageReference Include="Microsoft.AspNetCore.AzureKeyVault.HostingStartup" Version="2.0.2" />
    <PackageReference Include="Microsoft.AspNetCore.Cors" Version="2.2.0" />
    <PackageReference Include="Microsoft.AspNetCore.Mvc.Versioning" Version="3.1.2" />
    <PackageReference Include="Microsoft.Azure.KeyVault" Version="3.0.3" />
    <PackageReference Include="Microsoft.Azure.Services.AppAuthentication" Version="1.0.3" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Proxies" Version="2.2.1" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="2.2.1">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
    </PackageReference>
    <PackageReference Include="Microsoft.Extensions.Configuration.AzureKeyVault" Version="2.2.0" />
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="2.2.3" />
  </ItemGroup>

Answer 1

I'm not sure why or how this works, but I have stumbled on a solution:

1. Open the csproj
2. Edit <PackageReference Include="Microsoft.AspNetCore.App" /> to <PackageReference Include="Microsoft.AspNetCore.App" Version="2.2.0" />
3. Build > Clean Solution
4. Manually remove ALL bin and obj folders (even if they are only remotely related to the solution)
5. Build > Rebuild Solution
6. Edit <PackageReference Include="Microsoft.AspNetCore.App" Version="2.2.0" /> to <PackageReference Include="Microsoft.AspNetCore.App" />

That seemed to work for me, why a simple Clean Solution and Rebuild wasn't the answer is odd; but hopefully this will help someone else!