> C# libraries that use the protected attribute can be used transparently in F#.
Only if you don't need to write data types that need to be consumed by said libraries, as to express those types you need C# features.
Another two key examples are the recent trends from .NET team to depend on Roslyn and code generators, both not supported by F#, so the language can't be fully used in such workloads without a little bit of C# glue.
Really, F# might be from Microsoft, but the .NET team handles it as if it was a 3rd party guest language.
Only if you don't need to write data types that need to be consumed by said libraries, as to express those types you need C# features.
Another two key examples are the recent trends from .NET team to depend on Roslyn and code generators, both not supported by F#, so the language can't be fully used in such workloads without a little bit of C# glue.
Really, F# might be from Microsoft, but the .NET team handles it as if it was a 3rd party guest language.