F # return ICollection
I am working with a library built in C #. I've been working on porting some code to F #, but have to use quite a few base types from the C # lib.
One piece of code is to calculate a list of values and assign it to a public field / property in the class. Field is a C # class that contains two ICollection.
My F # code works fine and should return FQ Seq / List.
I have tried the following code snippets, each producing errors.
- The return type of the F # item is a type called restoreList with the type of restore list
-
A public field in a class that is a class that contains two ICollection objects
this.field.Collection1 = recoveries
This gives the error Expected type ICollection but has a list of recovery types
this.field.Collection1 = new ResizeArray<Recoveries>()
Provides the expected ICollection type, but ResizeArray
this.field.Collection1 = new System.Collections.Generic.List<Recoveries>()
Same errors as above expected by ICollection, but enter List
Any ideas? These operations seem to be valid from a C # perspective, and List / ResizeArray implements ICollection, so ... I'm confused how to assign a value.
I could change the type of the underlying C # library, but that might have different implications.
thank
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F # doesn't do implicit casting like C #. Therefore, even if it System.Collections.Generic.List<'T>
implements an interface ICollection
, you cannot directly set some ICollection
-typed property on an instance System.Collections.Generic.List<'T>
.
The fix is easy, but all you have to do is add an explicit transition to ICollection
in your ResizeArray<'T>
or System.Collections.Generic.List<'T>
before its assignment:
// Make sure to add an 'open' declaration for System.Collections.Generic
this.field.Collection1 = (recoveries :> ICollection)
or
this.field.Collection1 = (ResizeArray<Recoveries>() :> ICollection)
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