F#动态选项

尝试使此数据类型:

type ThreeWay = S of string | N of Decimal | D of DateTime

System.Object 类型:

open System
type Data =
    | Text of string
    | Number of string
    | Date of string
    with

    member x.Value
        with get() : Object option = 
            match x with
            | Text(value) ->
                if value.Length > 0 then Some(value :> Object) else None
            | Number(value) ->
                let (success, number) = Decimal.TryParse value
                if (success) then Some(number :> Object) else None
            | Date(value) ->
                let (success, date) = DateTime.TryParse value
                if (success) then Some(date :> Object) else None

要获取值:

let d = Number("123")
let v = d.Value
match v with
| Some(x) -> x :?> Decimal // <-- TYPE CAST HERE