F#类型扩展

//Intrinsic extension.
type typename with
    member self-identifier.member-name =
        body
    ...
[ end ]

//Optional extension.
type typename with
    member self-identifier.member-name =
        body
    ...
[ end ]

type ClassExtension() =
 member this.ShowBefore() = printfn"Class before extension"

//Define type extension.
type ClassExtension with
 member this.ShowAfter() = printfn"Class after extension"

let classExtension = new ClassExtension()
classExtension.ShowBefore()
classExtension.ShowAfter()