How to multi-target different compiler versions?

[thomhurst]

I've got a source generator that can target multiple framework versions.

If the user uses a collection expression (e.g. List<string> _list = []) then I need access to the newer compiler features, so I will need a newer codeanalysis package.

However, I also still want to be able to reference an older codeanalysis package for older sdks.

How would I do this?

I know I'll have to do some pre-processor if statements
E.g.

#if NET9_SDK
*** collection expression code ***
#endif

but I don't know what I would use to generate that pre-processor variable.

[thomhurst]

Found out. I can import the Microsoft.CodeAnalysis.* {Version}, and then package the analyzer under analyzers/dotnet/roslyn{Version}/cs