Question: How can I create a "soft dependency" between 2 projects

[TFTomSun]

Let's assume I have project A and project B. They have different incompatible TargetFrameworks, but the build of A depends on the build of B. I want to keep the delta compile compatibility, too. That means:

• no changes to both projects -> no build
• change in B -> Build of A triggers build of B first, then builds A
• change in A -> Only A builds

Is there a common approach to achieve that for all kind of SDK-style projects?

[xerif]

You can set project A to be dependent on B, without actually referencing B, using ProjectReference with:

• ReferenceOutputAssembly set to false
• SkipGetTargetFrameworkProperties set to true

This is loosely based on #3843

<!-- ProjectA.csproj -->
<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net20</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <ProjectReference Include="..\ProjectB\ProjectB.csproj">
      <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
      <SkipGetTargetFrameworkProperties>true</SkipGetTargetFrameworkProperties>
    </ProjectReference>
  </ItemGroup>
</Project>

<!-- ProjectB.csproj -->
<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netstandard2.1</TargetFramework>
  </PropertyGroup>
</Project>

This appears to fit your requirements, so:

• projects are incompatible (net20 cannot reference netstandard2.1)
• when changing something in A:
  • and building A => only A builds
  • and building B => nothing builds
• when changing something in B:
  • and building A => only B builds (nothing changed in A, so A doesn't)
  • and building B => only B builds

[TFTomSun]

@xerif thanks alot! SkipGetTargetFrameworkProperties was the property I didn't know before.

[rainersigwald]

Thanks @xerif! Closing this as that was a great answer.