Is it possible to set a condition to split windows and Linux platform logic?

[datoml]

Hello.
As far as I understand I am able to implement platform-specific logic based on the defined target frameworks.

The goal I am trying to achieve is to create a cross-platform library that is able to provide a USB communication layer for Windows, Linux and Android.

Implementing the Android part was easy because there is an existing TFM, in my case I used monodroid9.0, and I added a condition like the following in the csproj file.

<ItemGroup Condition=" '$(TargetFramework)' == 'monoandroid9.0' ">
	<Compile Include="Platforms\Android\*.cs" />
</ItemGroup>

But unfortunately, there is not a specific separation between Windows and Linux based on the available TFMs. Even .net5.0 has not specific TFMs for Linux.
I also found no informations why thats a case but I can imagine that its hard to find a common API for linux operation system?

I also looked up some projects from the dotnet runtime but I found no good solution so far.

After some further investigations it seems I can separat Windows and Linux logic with the RuntimeInformation.IsOSPlatform but this would result in a lot of IF ELSE statements.

Would it be possible to create some kind of "custom" TFM, so I am able to split the logic like I can do with Android?

A nice result would be to structure it like this in the csproj.

<ItemGroup Condition=" '$(TargetFramework)' == 'monoandroid9.0' ">
	<Compile Include="Platforms\Android\*.cs" />
</ItemGroup>

<ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0-windows' ">
	<Compile Include="Platforms\Windows\*.cs" />
</ItemGroup>

<ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0-linux' ">
	<Compile Include="Platforms\Linux\*.cs" />
</ItemGroup>

Thank you in advance. 😊