F# interop - Passing Immutable Collections & F# Collections into F# Functions from C#

[andrew-bauer-calibrated]

I have noticed that when I run F# functions in C# that return collections (like a List), they are returned as an FSharp variation (which is not a problem), however when I pass a collection into an F# function as a parameter, I can only pass in a mutable version.

Is there a way to pass in either the FSharp or Immutable variant? I know that I can just run ToList() on pass in, however I don't want to open the list up to possibly being mutated if it is already in an immutable format.

[huoyaoyuan]

they are returned as an FSharp variation (which is not a problem

This is not precise. The F# collection syntax provides F# collections. There are no limitations to use standard collections in F#.

Is there a way to pass in either the FSharp or Immutable variant? I know that I can just run ToList() on pass in, however I don't want to open the list up to possibly being mutated if it is already in an immutable format.

You can just declare the return type as F# collection. It will be seen as FSharp.Collections.List<T>. For immutability, you can use System.Collections.Immutable.ImmutableArray<T> and others.

[andrew-bauer-calibrated]

Thanks for the quick response.