F# provides Interface type. It provides pure abstraction. It is a collection of abstract methods.
type IEmployee =
abstract member ShowName : unit -> unit
type Manager(id:int, name:string) =
interface IEmployee with
member this.ShowName() = printfn "Id = %d \nName = %s" id name
let manager = new Manager(100,"RajKumar")
//manager.ShowName() // error: you can't directly access interface abstract method by using class object.
// so, we need to upcast class type object to interface type by using :> operator.
(manager :> IEmployee).ShowName()
