使用 Reflection 轉換為字串和從字串轉換

有時需要將 Discriminated Union 轉換為字串和從字串轉換：

module UnionConversion 
    open Microsoft.FSharp.Reflection
    
    let toString (x: 'a) = 
        match FSharpValue.GetUnionFields(x, typeof<'a>) with
        | case, _ -> case.Name

    let fromString<'a> (s : string) =
        match FSharpType.GetUnionCases typeof<'a> |> Array.filter (fun case -> case.Name = s) with 
        | [|case|] -> Some(FSharpValue.MakeUnion(case, [||])) :?> 'a)
        | _ -> None