Casting is a process of converting one type to another type. F# provides mainly two operators to deal with upcasting and downcasting. The :> operator is used to upcast object and :?> operator is used to downcast object.
Example :
type BaseClass() =
class
member this.ShowClassName()=
printfn "BaseClass"
end
type DerivedClass() =
class
inherit BaseClass()
member this.ShowClassName()=
printfn "DerivedClass"
end
let baseClass = new BaseClass()
let derivedClass : DerivedClass = new DerivedClass()
baseClass.ShowClassName()
derivedClass.ShowClassName()
let castIntoBaseClass = derivedClass :> BaseClass // upcasting
castIntoBaseClass.ShowClassName()
let castIntoDerivedClass = baseClass :?> DerivedClass // downcasting
castIntoDerivedClass.ShowClassName()
